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View Full Version : 5.56 77 Grain HP, as effective a sniper round as 308. 7.62?! Your thoughts


Mamluke
12-15-2011, 9:41 AM
5.56x45 77 Grain HP, fired from an AR platform rifle, heavy barrel 18~20 inch such as an MK-12. Can it be as effective as a dedicated .308 or 7.62x54 sniper rifle?

Pros:

Light weight, agility and mobility.
Full auto capability.
Can be deployed quickly and in All scenarios.
You run out of ammo, just borrow from the guy with the M4/AR15 ... :P


Cons:

Ultra Long range effectiveness.
Anything else?!

MK-12

http://www.fieldandstream.com/files/imagecache/photo-gallery/photo/23/021-DPMS-Mark-12.jpg

An interesting video on the subject:

jQG4_yOef-E


.... :popcorn: ....

evidens83
12-15-2011, 9:44 AM
Let's just say I wouldn't want to get head- shotted with either one ;)

MrPlink
12-15-2011, 9:46 AM
Let's just say I wouldn't want to get head- shotted with either one ;)

I make a much more general policy of trying to avoid being shot anywhere by anything PERIOD.

goodlookin1
12-15-2011, 9:49 AM
From how far?

What kind of 77gr bullet? What kind of .308 bullet?

How fast?

What's the Ballistic Coefficient?


There are so many questions that need answering. But generally, outside of 150-200 yards, NO, a 77gr 5.56 is not going to be as effective as a .308. Now if you're taking into consideration weight, speed, recoil, round capacity, etc....then you have to ask what will the primary purpose of the weapon be. If it's recon or scouting, sniping, then no. No one in their right mind would rather have a 5.56 than a .308 for this use. But if you're humping it for miles, doing a normal mission not knowing what distance any engagement will be, then you have something to talk/think about.

But this always ends up being a pissing match. What it usually comes down to is...(wait for it)...SHOT PLACEMENT.

JMHO.

SlickmisterN
12-15-2011, 11:17 AM
I think a better more fair comparison would be betwixt 6.5 Grendel, 6.8 SPC, and the .308 you mentioned. 5.56 and .308 were designed with completely differing goals.

Mamluke
12-15-2011, 11:19 AM
From how far?

What kind of 77gr bullet? What kind of .308 bullet?

How fast?

What's the Ballistic Coefficient?


There are so many questions that need answering. But generally, outside of 150-200 yards, NO, a 77gr 5.56 is not going to be as effective as a .308. Now if you're taking into consideration weight, speed, recoil, round capacity, etc....then you have to ask what will the primary purpose of the weapon be. If it's recon or scouting, sniping, then no. No one in their right mind would rather have a 5.56 than a .308 for this use. But if you're humping it for miles, doing a normal mission not knowing what distance any engagement will be, then you have something to talk/think about.

But this always ends up being a pissing match. What it usually comes down to is...(wait for it)...SHOT PLACEMENT.

JMHO.

Interesting and very well put analysis... so .308 is the undisputed king?!
Can one argue then that an MK-12 in 308 would still be a better choice than heavier bolt action/psl type rifles:

7.62x51

http://762precision.files.wordpress.com/2008/10/desert-operator-mk12-sniper1.jpg

http://www.armalite.com/Images/large%20images/Rifles/10TCBNFLARGE700.jpg

zfields
12-15-2011, 11:24 AM
I dunno, nothing says "Im going to ruin your F**k'in day" like a .30 cal bullet to me.

Merc1138
12-15-2011, 11:41 AM
Interesting and very well put analysis... so .308 is the undisputed king?!
Can one argue then that an MK-12 in 308 would still be a better choice than heavier bolt action/psl type rifles:

7.62x51

http://762precision.files.wordpress.com/2008/10/desert-operator-mk12-sniper1.jpg

http://www.armalite.com/Images/large%20images/Rifles/10TCBNFLARGE700.jpg

It's not the undisputed king, but it's been around for quite a while, is a NATO standard(well, 7.62x51 is), has more energy than 5.56, longer effective range than 5.56, and so on. There are of course other rounds besides .308 and 7.62 nato that can do as good a job or better(I'm not talking about .50bmg either) with varying ballistics as well.

Richard Erichsen
12-15-2011, 11:46 AM
5.56x45 77 Grain HP, fired from an AR platform rifle, heavy barrel 18~20 inch such as an MK-12. Can it be as effective as a dedicated .308 or 7.62x54 sniper rifle?

DMR rifle systems include 5.56x45 mm weapons, but dedicated sniper systems for the most part do not. Even 80 grain loads just don't have the terminal performance at ranges in excess of 600 meters, which tends to be where DMR rifles end and where sniper systems begin. At 1000 meters+ the more exotic calibers tend to be used.

Pros:

Light weight, agility and mobility.
Full auto capability.


Precision rifles for longer ranges generally require different compromises than weapons designed for full auto. In a platoon or squad, base of fire would be established by a different weapon.

Can be deployed quickly and in All scenarios.
You run out of ammo, just borrow from the guy with the M4/AR15 ... :P


A DMR equipped soldier firing deliberate, well aimed single fire will usually be the last weapon in the section to run dry. The benefit might be the ability for the riflemen in the squad to use the DMR's ammo rather than the other way around.


Cons:

Ultra Long range effectiveness.
Anything else?!


What is "ultra" long range? 1000 meters is bloody far as it is. If you want farther it won't likely be a .308 used for the role, but a .300 Win Mag, or the .338 Lapua or even the .50 cal if ranges demand 2000+ meters.


MK-12


If the desire was for converged DMR/LMG/SAW/AR caliber the debates rage about calibers that are either designed specifically to extend range and energy beyond 5.56x45 but fit within the constraints of the AR15 lower/OAL cartridge length limit, or alternative for throwing out the limitation and using a longer case mid way or as long as the 7.62x51 mm which has a certain appeal if you assume budgets for throwing out millions of perfectly good M16/M4 lowers.

There is still a solid role for the 7.62x51 mm which has the range and energy the 5.56x45 mm does not. A better bullet would improve upon the performance of the 7.62x51 mm, but there is already a substantial gap between the 5.56x45 mm Mk262 and the 7.62x51 mm M118LR.

R

Mamluke
12-15-2011, 11:55 AM
I dunno, nothing says "Im going to ruin your F**k'in day" like a .30 cal bullet to me.

LOL ... :P to me too!!!!

It's not the undisputed king, but it's been around for quite a while, is a NATO standard(well, 7.62x51 is), has more energy than 5.56, longer effective range than 5.56, and so on. There are of course other rounds besides .308 and 7.62 nato that can do as good a job or better(I'm not talking about .50bmg either) with varying ballistics as well.

Roger that ... :thumbsup:

The Turks use the 308 round on many of their standing army battle rifles, especially border patrols ... :D

http://www.mkek.gov.tr/Urunler/2YpPiplz.jpg

...

IrishPirate
12-15-2011, 11:55 AM
when you compare the rounds on some sort of graph, i'm sure there will be areas where they overlap, meaning that the ballistics are equal for an application (or at least produce the minimal ballistics required). However....the two will not be perfect shadows of each other and will occupy different areas of that graph meaning that one can do something or fulfill a need that the other can't.

so to answer your question....yes and no. at certain distances, taking certain things into consideration...the two will be equal. at other distances and with other factors to consider, one will be better than the other.

there's a reason why there's more than one caliber bullet...

Mamluke
12-15-2011, 12:00 PM
A DMR equipped soldier firing deliberate, well aimed single fire will usually be the last weapon in the section to run dry. The benefit might be the ability for the riflemen in the squad to use the DMR's ammo rather than the other way around.

There is still a solid role for the 7.62x51 mm which has the range and energy the 5.56x45 mm does not. A better bullet would improve upon the performance of the 7.62x51 mm, but there is already a substantial gap between the 5.56x45 mm Mk262 and the 7.62x51 mm M118LR.

R.

L BEEE DAM****

:King:

.... nough said ...

Mamluke
12-15-2011, 12:03 PM
so to answer your question....yes and no. at certain distances, taking certain things into consideration...the two will be equal. at other distances and with other factors to consider, one will be better than the other.

there's a reason why there's more than one caliber bullet...

TRULY PROLIFIC! I can't agree more!!!!

.....

GM4spd
12-15-2011, 1:05 PM
For over 300yds ---I prefer the bigger caliber,period,regardless of bullet weight. Pete

http://www.fototime.com/4EDC2C728C1547E/standard.jpg

http://www.fototime.com/57E4DB6DDDFF9DE/standard.jpg

http://www.fototime.com/DFB798DE9F0488B/standard.jpg

goodlookin1
12-15-2011, 1:10 PM
Interesting and very well put analysis... so .308 is the undisputed king?!
Can one argue then that an MK-12 in 308 would still be a better choice than heavier bolt action/psl type rifles:

7.62x51

http://762precision.files.wordpress.com/2008/10/desert-operator-mk12-sniper1.jpg

http://www.armalite.com/Images/large%20images/Rifles/10TCBNFLARGE700.jpg

No, .308 is not the undisputed king. And I am certainly no professional analyst. But within 100m, personally, I'd rather have a 5.56 due to it's speed and hydrostatic shock effect (the faster, the more damaging), and the increased round capacity and decreased weight. But they're both extremely damaging. And to be perfectly honest, I'd rather be spitting 55 grainers within 100m than 77gr pills that are going much slower. For all practical purposes though, 100m is a very close engagement. It doesnt matter which one you're shooting.....anything that ANY of those rounds hit is going to cause much pain.

I had a revelation about the AR-15 when I first shot my newly built .308 AR. The .308 was fun, but it had a lot of detriments to it compared to the AR-15 when considering anything inside 150-200m. It was heavy. It was bulky. It had a smaller round capacity (well, not in CA), it's more expensive (matters for us civvies), etc. When you mix that crap up with the fact that the AR-15 causes the same or just about as much damage as a .308 (depending on distance from 0-200m), it just doesnt make sense to build a .308 for CQB operation (to me, anything inside 200m). Mind you, the .308 does have a TON more energy when it hits, but energy isnt always the biggest factor in lethality. I'd take speed over energy every time, until the speed goes under about 2600 FPS. Once it goes below that speed, energy takes over and becomes more and more important as speed decreases.

The semi vs bolt argument is an old one. Pretty much it's generally recognized that semi's will typically exhibit slightly decreased accuracy and slightly less speed, but are much faster at follow-up shots and have less recoil. Bolts are generally a tad more accurate and can get the pill moving a bit faster, but at the expense of speed and recoil. So pick your hardware depending on your needs/wants. But the answer to "which one is better", especially when SHTF, in my book is thus: "The one that's in your hands" ;)


Oh and by the way: The first pic which is labeled 7.62 is actually a .223/5.56 :p. Look at the mag, look at the rounds on the ground....dead giveaway.

rojocorsa
12-15-2011, 1:25 PM
Oh and by the way: The first pic which is labeled 7.62 is actually a .223/5.56 . Look at the mag, look at the rounds on the ground....dead giveaway.


Not to mention, the proportions and length of the magwell.

FatalKitty
12-15-2011, 1:29 PM
how does the saying go?
if you can't reach it, call your SDM
if your SDM can't reach it, call arty
if arty can't reach it, who gives a ****

starsnuffer
12-15-2011, 2:38 PM
Interesting and very well put analysis... so .308 is the undisputed king?!
Can one argue then that an MK-12 in 308 would still be a better choice than heavier bolt action/psl type rifles:

7.62x51

http://762precision.files.wordpress.com/2008/10/desert-operator-mk12-sniper1.jpg

http://www.armalite.com/Images/large%20images/Rifles/10TCBNFLARGE700.jpg


WTF is that rifle dressed up like a "professional" wrestler for?

-W

OutlawDon
12-15-2011, 2:52 PM
5.56x45 77 Grain HP, fired from an AR platform rifle, heavy barrel 18~20 inch such as an MK-12. Can it be as effective as a dedicated .308 or 7.62x54 sniper rifle?


Here's a detailed and long-winded answer...

































NO.

You can't change physics.

chead
12-15-2011, 3:07 PM
The answer is no and it seems like a problem that doesn't need to be solved. .308 exists for a reason, use it.

Hoop
12-15-2011, 3:15 PM
My 77gr load is 2600fps out of my 16" AR whereas my usual 175gr load is 2450fps out of a 16" 308 AR. So it's 5% slower with a bullet that is more than twice the size...that's a lot more energy especially when you consider the higher ballistic coefficient...

Richard Erichsen
12-15-2011, 3:19 PM
For over 300yds ---I prefer the bigger caliber,period. Pete

http://www.fototime.com/57E4DB6DDDFF9DE/standard.jpg

http://www.fototime.com/DFB798DE9F0488B/standard.jpg

Nice L1A1.

R

stix213
12-15-2011, 3:19 PM
Doesn't 77gr typically not perform very accurately out of your typical 1:9 twist AR?

Mamluke
12-15-2011, 4:09 PM
No, .308 is not the undisputed king.... But within 100m, personally, I'd rather have a 5.56 due to it's speed and hydrostatic shock effect (the faster, the more damaging), and the increased round capacity and decreased weight. But they're both extremely damaging. And to be perfectly honest, I'd rather be spitting 55 grainers within 100m than 77gr pills that are going much slower. For all practical purposes though, 100m is a very close engagement. It doesnt matter which one you're shooting.....anything that ANY of those rounds hit is going to cause much pain.
The .308 was fun, but it had a lot of detriments to it compared to the AR-15 when considering anything inside 150-200m. It was heavy. It was bulky. It had a smaller round capacity... When you mix that crap up with the fact that the AR-15 causes the same or just about as much damage as a .308 (depending on distance from 0-200m), it just doesnt make sense to build a .308 for CQB operation Mind you, the .308 does have a TON more energy when it hits, but energy isnt always the biggest factor in lethality. I'd take speed over energy every time, until the speed goes under about 2600 FPS. Once it goes below that speed, energy takes over and becomes more and more important as speed decreases.

Very interesting, so for distances up to 200 meters an MK 12 with its 18/20 barrel is just as deadly yet more efficient .... I'd buy that 100%


Oh and by the way: The first pic which is labeled 7.62 is actually a .223/5.56 :p. Look at the mag, look at the rounds on the ground....dead giveaway.

Not to mention, the proportions and length of the magwell.

Yep, you're both right ... daaang!

how does the saying go?
if you can't reach it, call your SDM
if your SDM can't reach it, call arty
if arty can't reach it, who gives a ****

Good old Arty eh ... ;)

Here's a detailed and long-winded answer...


NO.

You can't change physics.

The answer is no and it seems like a problem that doesn't need to be solved. .308 exists for a reason, use it.

... but within 200 yards with the right barrel and velocity .... for outside that range, I agree ...

My 77gr load is 2600fps out of my 16" AR whereas my usual 175gr load is 2450fps out of a 16" 308 AR. So it's 5% slower with a bullet that is more than twice the size...that's a lot more energy especially when you consider the higher ballistic coefficient...

+1 however, it seems within 200 yards/meters the speed of the 5.56 round could be just as lethal & effective ... plus out of an 18~20 inch heavy barrel the 5.56 will be more than just 5% faster ... ;)

........... You guys are super knowledgeable, what a community here on CGN!

:thumbsup:

goodlookin1
12-15-2011, 5:01 PM
Very interesting, so for distances up to 200 meters an MK 12 with its 18/20 barrel is just as deadly yet more efficient .... I'd buy that 100%

It's a generalization, but yes. The 308 carries very little to no advantage up close. I say 200m, but it may be a little less....I'm not 100%. all I know is that sufficient hydrostatic shock requires 2600+ fps to significantly tear the tissue. Lower than that and you start poking holes and the 55gr FMJ stops tearing in half at the cannelure and instead does a through and through. OTM's help expansion at lower speeds, which causes more damage (think: wider hole, more damage) whereas fmj's dont expand at all (they're supposed to tear apart).

One of the things too about so many .308 tests is that they're still pitting all these upgraded 5.56 rounds against the 1950's designed 147 FMJ NATO round, which is very dated. Stick a different modern OTM type bullet in the .308 and it instantly becomes much more efficient in flight and lethality. But you still have the speed problem, in that a .308 isn't going as fast compared to a 5.56.

I'll say it again: I'll usually take speed over energy (within reason) just because of the damage caused by sufficient hydrostatic shock. But below 2600, I'd prefer more energy if I had the option. As someone else stated, out of a 16" barrel, it's hard to get the heavier bullets going fast enough to create that devastating hydrostatic shock, so more energy is preferred. Or just use a smaller projectile so it goes faster. There's a reason those varmints turn into pink mist with 40gr bullets (3500+ FPS!). But there is a happy medium: Too light and you risk no penetration. Too heavy and you have no speed.

There's a whole science on this....I suggest researching hydrostatic shock and energy, and how they affect overall performance of a round.

Peter W Bush
12-15-2011, 5:39 PM
How do you take speed over energy?! Those varmints turn into mist because of energy. Weight moving at a speed creates energy. There is NO question about whether a .223 is more powerful than a .308. 5.56 has less energy, less energy, and is more sensitive to wind. You're talking about 1800 J from a 5.56 vs 3500 J. out of a .308. The fact that there is a question about which is a better sniper round is strange to me.

Mamluke
12-15-2011, 5:52 PM
The fact that there is a question about which is a better sniper round is strange to me.

.... Ah ... my exact wording as I recall was as effective as; not "which is better" ...

..

..

..

BUT I SEE YOUR POINT .... :popcorn: ....

Bull's_eye
12-15-2011, 6:01 PM
Energy is directly proportional to speed. Energy = mass*velocity^2. As your speed drops, you need a bigger bullet in order to get more energy.

Peter W Bush
12-15-2011, 6:07 PM
.... Ah ... my exact wording as I recall was as effective as; not "which is better" ...

..

..

..

BUT I SEE YOUR POINT .... :popcorn: ....

You're right, sorry for the wording.

The 5.56 77gr (Mk262, etc.) is not as effective as something like a 175gr 7.62. My .308 shoots 175 SMKs at 2650 fps and 155 Scenars at 2900+. Actual Mk262 at around 2800 to 2880 fps. Physics just don't lie. BC of 77 gr SMKs is .36 and BC of 155s and 175 .30s is over .5. The .30s handle the wind better and retain more energy. They also have a shorter time to target. 308s are more effective.

goodlookin1
12-15-2011, 7:02 PM
How do you take speed over energy?! Those varmints turn into mist because of energy. Weight moving at a speed creates energy. There is NO question about whether a .223 is more powerful than a .308. 5.56 has less energy, less energy, and is more sensitive to wind. You're talking about 1800 J from a 5.56 vs 3500 J. out of a .308. The fact that there is a question about which is a better sniper round is strange to me.

My comment on taking speed over energy is a sum total of a lot of variables. You are correct in saying that "weight moving at speed creates energy", so you cant have one and not the other. But what I was saying (or trying to say) was that if given the option of having a higher speed and a lower energy VS a higher energy and a lower speed, I would take the high speed, lower energy round UNLESS the speed fell under around 2600 fps.

Energy is not the end-all be-all of lethality. An object that hits flesh at 2600+ fps creates devastating hydrostatic shock, the stretching of the surrounding tissue to the point that it tears apart.....this happens despite the amount of energy. Therefore, speed plays a major role in the effectiveness of a round outside of just energy. But you are talking strictly about POWER, which is usually in reference to energy. So yes, there is NO question that the .308 is much more powerful. But as I said previously, energy isnt everything in measuring lethality.

I do agree with you that it is strange that there is a question about which is better for a sniper round. No question, the .308. Every time. But that's because the distance of sniping is such that the impact velocity will be below the threshold necessary for hydrostatic shock creation. So when HS is taken out of consideration, like in .308 sniping, energy and bullet diameter becomes EVERYTHING in relation to lethality.

The question of 5.56 vs .308 effectiveness (not power) is ONLY a legitimate question in CQB situations, or imo inside of 150-200m. And a really good case can be made for using a 5.56 over a .308 in this situation for a myriad of reasons, wounding capabilities included.

HBchevelle68
12-15-2011, 7:10 PM
Depends what your trying to accomplish. If you talking about pure sniping. .308 with out a doubt, a 5.56 could never bring the same amount of stopping power as a .308.

But if your talking about a general patroling, i would take the 5.56. same reasons you mentioned. its light, fast able to cary more ammo.


The 5.56 isn't even close in terms of sniping

PachecoFTW
12-15-2011, 7:17 PM
What is a Sniper Rifle??

Mamluke
12-15-2011, 7:57 PM
... if given the option of having a higher speed and a lower energy VS a higher energy and a lower speed, I would take the high speed, lower energy round UNLESS the speed fell under around 2600 fps.

Same reasoning the Russians used for the adoption of the high speed 5.45 round over 7.62 ... amazing! But now that's for CQB situations


I do agree with you that it is strange that there is a question about which is better for a sniper round. No question, the .308. Every time...

I really wanna know WHO stated that question?! Again, I was asking if a 5.56 round, with a certain grain, fired from a heavy longer than usual barrel 18`20 inches 'Can be as effective as a .308?' I never said the word 'BETTER' ...

...The question of 5.56 vs .308 effectiveness (not power) is ONLY a legitimate question in CQB situations, or imo inside of 150-200m. And a really good case can be made for using a 5.56 over a .308 in this situation for a myriad of reasons, wounding capabilities included.

^^^^ So, is the answer YES (as effective as a 308) within a CQB range of UP TO 200 meters/yards?
... I think so!

What is a Sniper Rifle??

.... ^^^^ .... Its a double line fishing pole ....


:D

goodlookin1
12-15-2011, 8:05 PM
I really wanna know WHO stated that question?! Again, I was asking if a 5.56 round, with a certain grain, fired from a heavy longer than usual barrel 18`20 inches 'Can be as effective as a .308?' I never said the word 'BETTER'

It wasnt you. I think it was more implied by HOOP, Chead and OutlawDon, or misconstrued to mean in every situation, not just CQB. The problem was partially with your question too, since it didnt give a distance.

Your final answer is: YES, it can and will likely be just as effective, but pretty much only in CQB situations (I am arbitrarily throwing out the number 150-200m). As for DMR or sniping (we'll say 200m+), I'd definitely stick with a .308 as the increased energy will certainly play a role in increased chance of lethality.

Rockbranch
12-15-2011, 8:16 PM
"It's a generalization, but yes. The 308 carries very little to no advantage up close."

^what if you want to defeat body armor, cinder blocks etc., wouldn't the .308 be preferred 'up close' in that case?

HAVOC5150
12-15-2011, 8:34 PM
The mk 262 is the bullet that Travis Haley used in the video of him in Al-Najaf Iraq, when he was shooting from the top of the building farthest shot was 720 yrds. So it seems to me that the mk262 in the 556 platform is effective. Then again I am sure he would have rather had a Larue OBR etc.

IrishPirate
12-15-2011, 8:37 PM
It's a generalization, but yes. The 308 carries very little to no advantage up close. I say 200m, but it may be a little less....I'm not 100%. all I know is that sufficient hydrostatic shock requires 2600+ fps to significantly tear the tissue.where are you getting that info from??? lots of bullets don't travel that fast but produce enough hydrostatic shock to kill...what kind of tissue are you talking about too?? there are several types of tissue in the body. Lower than that and you start poking holes and the 55gr FMJ stops tearing in half at the cannelure and instead does a through and through. OTM's help expansion at lower speeds, which causes more damage (think: wider hole, more damage) whereas fmj's dont expand at all (they're supposed to tear apart). So why is it then that a .308 will take down a deer no problem under 200m but 7mm's tend to go straight through? 7mm is traveling much faster so shouldn't it drop the deer??

One of the things too about so many .308 tests is that they're still pitting all these upgraded 5.56 rounds against the 1950's designed 147 FMJ NATO round, which is very dated. Stick a different modern OTM type bullet in the .308 and it instantly becomes much more efficient in flight and lethalityvery true!!. But you still have the speed problem, in that a .308 isn't going as fast compared to a 5.56.but it's traveling PLENTY fast enough to do lethal damage from 0-1000yds

I'll say it again: I'll usually take speed over energy (within reason) just because of the damage caused by sufficient hydrostatic shock. But below 2600, I'd prefer more energy if I had the option lost on where you're getting this info :confused:. As someone else stated, out of a 16" barrel, it's hard to get the heavier bullets going fast enough to create that devastating hydrostatic shock, so more energy is preferred but if force=massXacceleration, how do you get more force without going faster??. Or just use a smaller projectile so it goes faster. There's a reason those varmints turn into pink mist with 40gr bullets (3500+ FPS!). But there is a happy medium: Too light and you risk no penetration. Too heavy and you have no speed.

There's a whole science on this....I suggest researching hydrostatic shock and energy, and how they affect overall performance of a round.

^bold^

i'm not doubting you, i'm just confused. can you elaborate? I understand the principle of hydrostatic shock, but how the .308 doesn't produce enough doesn't seem right to me...especially if the bullet weighs almost 3x as much and the speed difference isn't more than 3x as fast...

zfields
12-15-2011, 11:42 PM
^bold^

i'm not doubting you, i'm just confused. can you elaborate? I understand the principle of hydrostatic shock, but how the .308 doesn't produce enough doesn't seem right to me...especially if the bullet weighs almost 3x as much and the speed difference isn't more than 3x as fast...

It sounds like he is mixing up hydrostatic shock and fragmentation.

Sent from my Incredible 2

phish
12-16-2011, 12:04 AM
this thread has provided endless hours if entertainment, thank you

goodlookin1
12-16-2011, 6:59 AM
where are you getting that info from??? lots of bullets don't travel that fast but produce enough hydrostatic shock to kill...what kind of tissue are you talking about too?? there are several types of tissue in the body.
There are so many variables in whether or not you will get a kill or only a slight injury. Specifically HS is a highly debated topic, and often internet folklore has made it something it is not. All it is is the stretching of tissue in the temporary cavity. IF the speed is fast enough, AND there is enough energy to push the bullet deep enough, it iwll create a temporary cavity as such a force and speed that the tissue stretches beyond the breaking point of elasticity and creates what is called the "permanent cavity". You will see much writing of pistol HS on the internet, but it's all lies. No typical pistol bullet is going fast enough to create a permanent cavity, other than the hole that the bullet creates. So it goes: The wider the diameter of the bullet, the bigger the whole = more damage. Then energy comes into play, along with and penetration. But as for your direct question, the tearing "permanent cavity" type of HS generally BEGINS at around 2300 fps, and the fragmentation of an M193/M855 bullet happens at a MINIMUM of 2600 fps and more typically at 2700. But pretty much, if the bullet is going slower than 2300 fps, it's not creating lethal HS, only stretching the tissue and then returning in tact.

So why is it then that a .308 will take down a deer no problem under 200m but 7mm's tend to go straight through? 7mm is traveling much faster so shouldn't it drop the deer??
Not sure where you get this info. 7mm has taken many a deer with no problems. In fact, the 7mm Rem Magnum is faster than the .308 and often has an identical bullet weight, thus creating more energy (even more than a .30-06). With a good expanding hunting bullet, a through and through without expansion and lethal HS is not likely to happen. Might want to change your bullet choice ;)

but it's traveling PLENTY fast enough to do lethal damage from 0-1000yds
"Lethal" damage is a subjective term. Sure, if placed in the right spot it can be lethal. Heck, there was a kid in El Dorado hills just last week who died from a pellet gun shot to the chest! A tiny 20gr pellet moving at 1000 fps. He ran home and collapsed right after telling his parents. Very sad. It hit somewhere on his heart. But it goes to show that if you hit anything in the right place with the smallest and weakest of rounds, it can be lethal. But we're talking about averages here, not extremely remote chances. Likewise, at 1000 yards, a 5.56 can kill something, but the chances of it doing so (vs just wounding) are GREATLY diminished. The lethality and power of the 5.56 comes from it's speed, not energy. Once it's lost it's speed, the bullet is so small that there is little energy behind it to TYPICALLY do enough damage to cause reliable damage. At 1000m, it's probably the same as shooting something with a 10/22 at 200m (just an estimation....dont quote me on that). Even the .308 at 1000m loses it's luster and a shooter would be better served with a .338LM or even a .300WM.....let alone the 5.56!

lost on where you're getting this info .
All sorts of different documents and findings. Military, FBI, private tests, etc.

but if force=massXacceleration, how do you get more force without going faster??
I said "heavier bullets" out of a 16" barrel. Either get a longer barrel, or use a lighter bullet to increase speed. Increasing or decreasing the bullets weight wont give you much of a difference in energy in CQB, but it WILL affect long range energy due to the increased Ballistic Coefficient of the heavier, longer bullet (it retains it's speed better over longer distances, thus giving more energy). The lighter bullets will slow down faster and drop your energy quicker. But again, in CQB, i'd take the higher speed and lower energy.

i'm not doubting you, i'm just confused. can you elaborate? I understand the principle of hydrostatic shock, but how the .308 doesn't produce enough doesn't seem right to me...especially if the bullet weighs almost 3x as much and the speed difference isn't more than 3x as fast...
The .308 can/does produce significant HS. But it is starting off at the muzzle much slower than the 5.56, thereby making the range of effective HS for the .308 decrease. Of course, a longer barrel, a hotter load and also a lighter bullet can extend the range of effective HS.....same with the 5.56. Furthermore, there is not a linear correlation to effective HS between energy and speed. In fact, energy doesnt really play much of a role in HS (okay a little, but not as much as speed). The 3x weight of the bullet, but decreased muzzle velocity, translates to basically 2x the energy of .308 over 5.56. (M855 vs M80) at the muzzle. But that 2x energy doesnt translate to more or better HS at all because it is going slower. In the HS world, a 350 fps increase is a night and day difference (5.56 3100fps vs .308 2749fps [20" bbl?]) and will greatly increase cavitational damage (also due in part to the yaw of the bullet after impact).


In the end, I would argue that both 5.56 and .308 are similarly effective in CQB operations, giving the advantage to the 5.56 due to increased round capacity, decreased recoil and decreased weight. But anything outside of this realm of the battlefield and the .308 takes the cake every time, ESPECIALLY when using better, more modern designed bullets. This is my own opinion....take it with a grain of salt :cool:.

fdesalvo
12-16-2011, 7:35 AM
If you put a pane or two of glass between you and your enemy, the 5.56 won't be of much use.

"It's a generalization, but yes. The 308 carries very little to no advantage up close."

^what if you want to defeat body armor, cinder blocks etc., wouldn't the .308 be preferred 'up close' in that case?

Hoop
12-16-2011, 8:14 AM
This thread is turning into comedy.


+1 however, it seems within 200 yards/meters the speed of the 5.56 round could be just as lethal & effective

I'm sure it works but "just as lethal & effective" will be debatable...

starsnuffer
12-16-2011, 8:25 AM
Dead is dead. When you figure out how to kill something more deader, you let us know.

IMHO, if someone has the job of killing someone else for a living, they probably have a good understanding about using the right tool for the right job. Sometimes (despite redneck wisdom), a hammer isn't always the right tool. Sometimes it is.

-W

Army GI
12-16-2011, 2:46 PM
Different calibers, different applications. The .223 can never be a .308. Only the .308 can be a .308.

chicoredneck
12-16-2011, 3:04 PM
You can't get much deader than dead. Central nervous system hits are the only way to instantly drop someone.

308 has the potential to penetrate more, it also can stay super sonic a little further. If that matters to the user then it is more effective. If it does not then it doesn't offer anything over 556 IMO.

POLICESTATE
12-16-2011, 3:11 PM
7.62 > 5.56 at range, even the terrorists know that.

IrishPirate
12-16-2011, 6:25 PM
There are so many variables in whether or not you will get a kill or only a slight injury. Specifically HS is a highly debated topic, and often internet folklore has made it something it is not. All it is is the stretching of tissue in the temporary cavity. IF the speed is fast enough, AND there is enough energy to push the bullet deep enough, it iwll create a temporary cavity as such a force and speed that the tissue stretches beyond the breaking point of elasticity and creates what is called the "permanent cavity". You will see much writing of pistol HS on the internet, but it's all lies. No typical pistol bullet is going fast enough to create a permanent cavity, other than the hole that the bullet creates. So it goes: The wider the diameter of the bullet, the bigger the whole = more damage. Then energy comes into play, along with and penetration. But as for your direct question, the tearing "permanent cavity" type of HS generally BEGINS at around 2300 fps, and the fragmentation of an M193/M855 bullet happens at a MINIMUM of 2600 fps and more typically at 2700. But pretty much, if the bullet is going slower than 2300 fps, it's not creating lethal HS, only stretching the tissue and then returning in tact.

ok, if you had mentioned the PERMANENT cavity, that would have made more sense when talking about speed. I can agree with that

Not sure where you get this info. 7mm has taken many a deer with no problems. In fact, the 7mm Rem Magnum is faster than the .308 and often has an identical bullet weight, thus creating more energy (even more than a .30-06). With a good expanding hunting bullet, a through and through without expansion and lethal HS is not likely to happen. Might want to change your bullet choice ;)

I don't shoot a 7mm but i know plenty of people who do and say they get more through and throughs than anything. The deer definitely drops, but only after running for a while. Talked to LOTS of hunters too when i validate deer that have the same experience. Not sure what type of ammo their using though...i'm sure it plays a big part in that.

"Lethal" damage is a subjective term. Sure, if placed in the right spot it can be lethal. Heck, there was a kid in El Dorado hills just last week who died from a pellet gun shot to the chest! A tiny 20gr pellet moving at 1000 fps. He ran home and collapsed right after telling his parents. Very sad. It hit somewhere on his heart. But it goes to show that if you hit anything in the right place with the smallest and weakest of rounds, it can be lethal. But we're talking about averages here, not extremely remote chances. Likewise, at 1000 yards, a 5.56 can kill something, but the chances of it doing so (vs just wounding) are GREATLY diminished. The lethality and power of the 5.56 comes from it's speed, not energy. Once it's lost it's speed, the bullet is so small that there is little energy behind it to TYPICALLY do enough damage to cause reliable damage. At 1000m, it's probably the same as shooting something with a 10/22 at 200m (just an estimation....dont quote me on that). Even the .308 at 1000m loses it's luster and a shooter would be better served with a .338LM or even a .300WM.....let alone the 5.56!

again, after the permanent cavity thing, this makes more sense. I thought you were saying there wasn't enough HS to kill. definitely agree with .338LM or .300WM being better suited. Love both those rounds!! :D

All sorts of different documents and findings. Military, FBI, private tests, etc.

got any links? sounds like interesting reads....

I said "heavier bullets" out of a 16" barrel. Either get a longer barrel, or use a lighter bullet to increase speed. Increasing or decreasing the bullets weight wont give you much of a difference in energy in CQB, but it WILL affect long range energy due to the increased Ballistic Coefficient of the heavier, longer bullet (it retains it's speed better over longer distances, thus giving more energy). The lighter bullets will slow down faster and drop your energy quicker. But again, in CQB, i'd take the higher speed and lower energy.

no argument here, must have missed the 16" part.

The .308 can/does produce significant HS. But it is starting off at the muzzle much slower than the 5.56, thereby making the range of effective HS for the .308 decrease. Of course, a longer barrel, a hotter load and also a lighter bullet can extend the range of effective HS.....same with the 5.56. Furthermore, there is not a linear correlation to effective HS between energy and speed. In fact, energy doesnt really play much of a role in HS (okay a little, but not as much as speed). The 3x weight of the bullet, but decreased muzzle velocity, translates to basically 2x the energy of .308 over 5.56. (M855 vs M80) at the muzzle. But that 2x energy doesnt translate to more or better HS at all because it is going slower. In the HS world, a 350 fps increase is a night and day difference (5.56 3100fps vs .308 2749fps [20" bbl?]) and will greatly increase cavitational damage (also due in part to the yaw of the bullet after impact).

i would still think that the .308 would produce sufficient HS in CQB because of the size of the bullet, but i do agree that the 5.56 shines in CQB versus other applications

In the end, I would argue that both 5.56 and .308 are similarly effective in CQB operations, giving the advantage to the 5.56 due to increased round capacity, decreased recoil and decreased weight. But anything outside of this realm of the battlefield and the .308 takes the cake every time, ESPECIALLY when using better, more modern designed bullets. This is my own opinion....take it with a grain of salt :cool:.

taking other stuff into consideration, there's still no clear winner in my eyes. But there's enough good stuff about each round that i doubt either will be replaced anytime soon (though i've been hearing that the military does want to replace the 5.56 with something that has more power :shrug: )

elSquid
12-16-2011, 6:55 PM
Dead is dead. When you figure out how to kill something more deader, you let us know.


http://www.youtube.com/watch?v=8hID4xK2Fo0

:shifty:

-- Michael

thmpr
12-16-2011, 7:04 PM
Think about this: You take your guess which one wins in the "damage" factor.

mass X velocity = force

175 grains x 2500 fps =

77 grains x 2600 fps =

goodlookin1
12-16-2011, 7:08 PM
i would still think that the .308 would produce sufficient HS in CQB because of the size of the bullet, but i do agree that the 5.56 shines in CQB versus other applications
It certainly does create "sufficient" HS at CQB distances. But I/we were diving more into which round would give better HS (thus being more effective). I would say that looking strictly at wounding ability, the HS of the 5.56 and the energy of the .308 is likely/usually very comparable IN CQB distances. I'm sure others share differing opinions.

taking other stuff into consideration, there's still no clear winner in my eyes. But there's enough good stuff about each round that i doubt either will be replaced anytime soon (though i've been hearing that the military does want to replace the 5.56 with something that has more power :shrug: )
You're right. There is no clear winner when it comes to CQB. That's why there are these arguments that parallel the heated level of DI vs Piston debates! But I cant tell you this: Neither round is going anywhere anytime soon, even though IMO they should replace it in favor of something like a 6.5/6.8mm. Because our mil doesnt have an unlimited budget, "good enough" plays a large part in the decision making ;)

russ69
12-16-2011, 8:45 PM
....DMR rifle systems include 5.56x45 mm weapons, but dedicated sniper systems for the most part do not. Even 80 grain loads just don't have the terminal performance at ranges in excess of 600 meters...

Yeah, off the the top of my head, the 80 grain bullets make it to 600 yards and not too much further. Even with VLD bullets (very low drag) the 223 just can't make 1000 yards (with top, match winning accuracy). They come darn close I hear if the wind is still but as soon as there is a puff, they start dropping points.

LooseCannon
12-16-2011, 9:16 PM
mass X velocity = force

That part's wrong.

Mass[kg] * Acceleration[m/s^2] = Force[N]
and
Mass[kg] * Velocity[m/s] = Momentum [kg*m/s]

And really just to muddy the water a little more "Energy" is based on a force applied to an area [Newton*meter or Joule], not the same as momentum that most talk about. :)

LC

Edit: not to be a pain in the a** just want to clarify the conversation.

Rockbranch
12-16-2011, 9:27 PM
"If you put a pane or two of glass between you and your enemy, the 5.56 won't be of much use."

as if in "real life" all your shots will be stationary targets in the clear with giant flags that read "please shoot me".

most engagements involve some type of cover, hence my question about cover, armor, etc. then again 99% of us won't be involved in said engagements so wgas-

UserM4
12-16-2011, 9:37 PM
For rapid fire, 5.56
For well aimed precision shots, 7.62
/thread

Mamluke
12-17-2011, 12:27 PM
Here's a cool video on 'light' 308 rifles
7.62x51 Nato FAL & LWRC REPR

8sm4oxoQbes

.............

Michaeln
01-02-2012, 5:04 PM
I'm curious as to the effect of the heavier 77 gr bullet in a 3 gun competition scenario. I have been purchasing factory 55 gr ammo for practice and competition because it's much less expensive to shoot. Would I be much better off, accuracy wise, to reload 77 gr. bullets instead of the current 55 I've been using? I have a very similar gun to the sniper mk 12 they talk about in the attached video. It's an 18" DMR LWRC M6a3.

In your opinion, would the 77gr. bullet be more accurate than the 55's I'm using now?

Mamluke
01-02-2012, 5:29 PM
In your opinion, would the 77gr. bullet be more accurate than the 55's I'm using now?

NO! The 77 Grain round will carry more punch & transfer more kinetic energy upon impact. It doesn't have a bearing on accuracy.

............

Hoop
01-02-2012, 5:46 PM
In your opinion, would the 77gr. bullet be more accurate than the 55's I'm using now?

Yes if you do it properly. You are talking about handloads with a match bullet vs. mass produced stuff with a so-so bullet.

Depending on the groups you are getting now vs. what you hope to get it may or may not be worth it.

chrisf
01-02-2012, 5:52 PM
Let's just say I wouldn't want to get head- shotted with either one ;)
Foreal.

Mamluke
01-02-2012, 6:23 PM
Foreal.

... lol ....

military snipers train for head shots and upper body ...
.... yeah, for real ... :D

BrianRodela
01-02-2012, 6:46 PM
I hate to point this obvious question,....When was the last time ANYONE ever actually shot at another human being. Lets face it, the most we will ever see any threat, for the vast majority of us, is the menacing target at the range. IMHO, get what you can afford and be proficient with it. If it ever comes to SHFT where we have to consider shooting at a person (as a citizen and I hope to God it never comes to that), we have far more significant issues to deal with.

Nuff said

The Chief

Mamluke
01-02-2012, 7:15 PM
I hate to point this obvious question,....When was the last time ANYONE ever actually shot at another human being. Lets face it, the most we will ever see any threat, for the vast majority of us, is the menacing target at the range. IMHO, get what you can afford and be proficient with it. If it ever comes to SHFT where we have to consider shooting at a person (as a citizen and I hope to God it never comes to that), we have far more significant issues to deal with.

Nuff said

The Chief

Dude, what planet are you at?! ... I come across these all the time:

http://acidcow.com/pics/20100829/different_types_of_aliens_09.jpg

... lol ......... :D


........ ;)


...

RONIN.
01-02-2012, 7:29 PM
Here's a detailed and long-winded answer...

































NO.




You can't change physics.

nothing more needed to be said.. unless OP wants a lesson in ballistics..

Norsemen308
01-02-2012, 8:44 PM
uhhh.... no....

sorry laws of physics is what I am gonna stay with.. if this was true dont you believe the military would have made this happen already??? the military drops millions of dollars EACH YEAR... on weapon research... especially with all the crap the taliban has been giving them with making sure enemy positions are at the magical 600 mark....

762x51 will not be unseated for A LONG TIME.... the EBR that they are rolling out with now a days proves theyw ill not be going away any time soon...

zfields
01-02-2012, 10:18 PM
NO! The 77 Grain round will carry more punch & transfer more kinetic energy upon impact. It doesn't have a bearing on accuracy.

............

less wind drift ( though not by much ), and longer bearing surface depending on bullet construction can both lead to better accuracy.

Droppin Deuces
01-02-2012, 10:32 PM
I dunno, nothing says "Im going to ruin your F**k'in day" like a .30 cal bullet to me.

The .22LR might have something to say about that! I believe that round has ruined the days of more people than any other caliber.