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

[POLICESTATE]

7.62 > 5.56 at range, even the terrorists know that.

[IrishPirate]

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!!

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 .

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 )

[elSquid]

Dead is dead. When you figure out how to kill something more deader, you let us know.

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

-- Michael

[thmpr]

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]

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 )

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]

....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]

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]

"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]

For rapid fire, 5.56
For well aimed precision shots, 7.62
/thread

[Mamluke]

Here's a cool video on 'light' 308 rifles
7.62x51 Nato FAL & LWRC REPR



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

[Michaeln]

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]

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]

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]

Let's just say I wouldn't want to get head- shotted with either one

Foreal.

[Mamluke]

Foreal.

... lol ....

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