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

[rojocorsa]

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]

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]

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

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

-W

[OutlawDon]

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]

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]

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]

For over 300yds ---I prefer the bigger caliber,period. Pete

Nice L1A1.

R

[stix213]

Doesn't 77gr typically not perform very accurately out of your typical 1:9 twist AR?

[Mamluke]

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 . 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!

[goodlookin1]

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]

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]

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" ...

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BUT I SEE YOUR POINT .... ....

[Bull's_eye]

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]

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

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BUT I SEE YOUR POINT .... ....

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]

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.