What the M855 really does

[MTMilitiaman]

Okay so if we first admit that immitation is the sincerest form of flattery, and that the 5.45 is an immitation of the 5.56, and that majority rules in this regard, then we must also compare the weapons systems and acknowledge that while very few people have attempted to copy the operating system of the M16, there are numerous such efforts to do so with the Kalashnikov. Therefore, the AK is the better weapon because it is immitated most often, right? If some of you object, then you must also admit that such assumptions are invalid when discussing cartridges.

Secondly, regarding 7.62x39 v 5.45x39, the 5.45 still relies on tumbling as its primary wounding mechanism. The bullet if fairly long, however, being sufficently heavy for caliber, and having a large air pocket in the nose, that when tumbling it tends to displace a fair amount of tissue. The Yugo M67 ball round for the 7.62x39 behaves in a much similar manner, also possessing an air pocket in the nose, and according to Fackler creates wound channels nearly identical to those of the 5.45mm, tyically yawing within ~9 cm of ballistic geletin--a full 17 cm sooner than the predecessor M43 ball round. Wolf FMJs are constructed like the Yugo round and when discected will show the air pocket comprising the forward 1/3 of the bullet's length. The only difference is that even if these rounds don't yaw, they are at least .311 caliber.

Thirdly, you are comparing bullets designed to tumble and fragment quickly in flesh with those designed with relatively little attention give to this. Try comparing bullets of equal design, and it again becomes absurd to claim the 5.56 is as effective as any 7.62mm. Put a 75 gr Vmax in the 5.56, 123 gr Vmax in a 7.62x39, and a 155 gr Vmax in a 7.62x51, and the effectiveness, given equal shot placement, will be in that order. Fackler provides such evidence by showing the effectiveness of West German 7.62x51 ball ammo, which had a different alloy in the jacket, making it more brittle. It tended to act in tissue much like the M193, but with wound channels fully twice the diameter of those experienced with the 5.56.

Finally, if you have a round that does twice the damage, then you don't really need twice the ammo. Wrapping everything up, the 5.56 may or may not fragment, but the 7.62mm isn't getting any smaller.

 

[Cosmoline]

The next misconception is that 5.56mm is ineffective. According to Fackler, the 5.56mm bullet does considerably more damage than a 7.62mm bullet within its design envelope. People rant about 7.62 being so effective but the only people who shoot it are snipers and machine gunners.

Only if you artificially limit yourself to FMJ bullets. The advantage of the 5.56 comes from its inherent failure to maintain its structure at high speeds. This is ONLY an advantage because of the Hague Convention. If you remove the artificial legal constraints, the 5.56 resumes its place as a gopher round. This is why the only people who fire the 7.62/.308 are NOT snipers and machine gunners. It's widely used as a hunting round, especially in semiautomatic rifles and short action bolt guns.

 

[Don't Tread On Me]

• FAL having better stand-off range? Only if you can hit someone 700 yards away with it. Consider that an AR-15, with handloads and a FF tube can score headshots at 500 yards(not that you would go for them, but the accuracy is there), and that with 30 minutes of training an 10 year old girl can be trained to score COM hits at 400...I seriously doubt a FAL is necessarily a better "stand off" weapon just because it is .308. Both being scoped, the AR is easier to shoot and is more accurate with less hassle involved. Not to mention, you won't lose your sight picture with the AR, thus you can deliver a constant barrage of well-aimed, precision fire at any target.
  
  
• If slow, well aimed shots won violent armed confrontations, then we'd all be better served with muzzle loaders. Sorry, but spray is superior to slow fire. With a 5.56 you can spray without having to pray, thanks to the low-recoil. The name of the game is the fastest, highest volume fire that you can direct accurately enough to get hits. "Good enough" counts. Don't need 10 rings, just hits.
  
  
• If the 7.62x39 were such a great 1 shot manstopper, the AK-47 wouldn't have been select fire. No need for full auto when .30 cal lets you do the job with 1 well aimed shot. Also, full auto is a waste of bullets when you should be aiming in semi-auto mode instead. Dumb Soviets! They are wasting 1-shot stopping power by building a select fire rifle.
  
  
• An AR-15 can be every bit the "marksmans" rifle as any .30 cal. If you can take the time to aim and guarantee 1st shot hits, then you can do that with an AR too. The question then becomes, is the 5.56 good enough with one hit? I think so. I dunno too many people who will just shake off a chest hit from a .223...likewise they won't fare well with a x39 or 545 or .308 going through them either. However..........
  
  
• .........anything worth shooting is worth shooting twice - regardless of caliber. More holes = better. Caliber is secondary.

 

[Onmilo]

M855 62 grain penetrator ball cartridge.
I have never used this stuff to pop a human being, what I know about it comes from the target range where I have sent more than a few of these rounds down range.

What I can tell you is the stuff isn't all that accurate.
Even the new improved versions just don't group all that well, especially if the range exceeds 300 meters and I thought that was one of the big brew hoo hoos about this cartridge.
The ability to shoot out to 800 meters and retain enough energy to penetrate a steel helmet.
All well and good with the exception that most lots of this ammunition from a number of different global sources cannot group well enough to hit a helmet at that distance.

The US Army still teaches battlefield zero of 300 meters and it may be a good thing.
Heck, I am begining to agree with several sources that the M16 combat rifle really does not need that tricky full adjustment rear sight.
The M16/M16A1 semi fixed sight was rugged and more than adequate for the combat ranges the rifle is normally used to engage.

There are suppossed to be fixes to this problem and newer lots tend to group better but if groupability is so much better then why does the Military issue 77 grain Black Hills ammunition to select groups of Servicemen who are most likely to go in harms way??

Leave the long range stuff to the Ma Deuce and the artillery.

 

[Stiletto Null]

I think it's Nosler, actually.

It's for designated marksmen and such (well, I think Marines are trying to make it standard for everybody, but that's the MARINES ), who get the fancypants rifles and higher-powered optics.

 

[Jeff White]

Secondly, regarding 7.62x39 v 5.45x39, the 5.45 still relies on tumbling as its primary wounding mechanism.

All spitzer bullets tumble. It's basic physics, when the weight of the projectile is in the back and it hits something, that weight is going to attempt to move forward and the bullet will tumble. The big difference in terminal effects is how far the bullet penetrates before it yaws completely around and ends up base first.

I think it's Nosler, actually.

Black Hills makes the MK262 and MK262 MOD 0.

Jeff

 

[MTMilitiaman]

Jeff, I know. The implication from the original poster was that the 5.45mm relied on fragmentation similar to the 5.56. My understanding is that this is incorrect, and the round is designed to accelerate tumbling in soft tissue by either causing the front of the projectile to flatten upon impact, or to allow inertia to move the core, and thus the center of gravity, forward upon impact. This does not rely on fragmentation and is as such less reliant on velocity, according to my understanding.

 

[Don't Tread On Me]

MTmillitiaman, I've wondered that very same thing. The 5.45 is built with a very solid and hard jacket (like the Wolf .223) and probably doesn't fragment.

It's been a while since I've read through all those Fackler docs, so it might all be there.

Here's the question, if the bullet is designed to tumble only, is there a speed threshold where this effect ceases to occur? Would sending it out at 3,330fps prevent tumbling? Or would sending out at 1,800fps prevent it? Or does it tumble regardless of velocity?


As for 5.56...here's the beauty of the new bullets. The new heavies for the .223 not only fragment, but they've pretty much added the whole early-yaw tumble effect of the 5.45. Best of both worlds. Have you seen the length difference between the Hornady 68gr HPBT and a standard 55gr FMJ? It is quite a huge difference! The Hornady 68 is like a long skinny spike, while the 55 looks more like a normal bullet. The 68 is very 5.45'ish in a way. If it doesn't fragment, it will certainly yaw because it is as butt heavy as you can get in that design.


The heavier .223 bullets are longer. Being that diameter is constant and unchanging, adding weight forces them to be longer. Most of that weight remains in the center to rear of the bullet and becomes part of the boattail. It cannot be added to the front a whole lot because the .223 cartridge must still fit into a USGI magazine. The 75 hornady is about the same length as the 68. The extra 7gr is added to the boattail area and the profile of the nose isn't as sharp on the 75.

The lighter .223 bullets go into a case pretty much at or a hair deeper than the neck. The heavies go past the neck all the way to the bottom of the shoulder of the case often pushing into the powder. Some powders and 77's create compressed charges. The nose of these bullets are left hollow and they now have 5.45 properties.


If I had to guess, if these bullets were built with strong jackets, they would tumble just like the 5.45 (maybe worse). Don't confuse the fact that they tumble very quickly in tissue then explode because of lateral forces on the bullet (fragmentation). That doesn't mean the only wounding factor involved is simple fragmentation. If they didnt' fragment, they'd probably tumble like the 5.45.


The 77's and 75's begin to yaw just a few CM's upon entering tissue. Quite impressive compared to the 5.45. More weight, quick tumble, large fragmentation. These are about as good as it gets terminal performance-wise for the small-bore world.

 

[Bartholomew Roberts]

Here's the question, if the bullet is designed to tumble only, is there a speed threshold where this effect ceases to occur? Would sending it out at 3,330fps prevent tumbling? Or would sending out at 1,800fps prevent it? Or does it tumble regardless of velocity?

My understanding (and I always welcome input from those who have a better foundation in the subject) is that all non-expanding bullets tumble at all velocities but that as bullet shape and velocity change, WHERE it tumbles may be an important difference. It may tumble so late that for practical purposes it won't tumble inside most deer-sized objects. I do know that 9mm FMJ will tumble and have seen X-rays of the phenomenon inside gunshot victims.

As I understand it, tumbling is a basically a stabilization issue. In order to put a fast enough twist on a bullet for it to stay stable inside a mostly water medium like tissue, the bore would need a twist that would make it look like it was threaded. Since it doesn't have this stabilization, any non-expanding bullet that has more weight behind the nose than in front of it yaws due to center of gravity. Expanding bullets don't usually yaw because the center of gravity moves as the bullet expands.

 

[atblis]

Hmmm

Fragmenting 7.62 > Fragmenting 5.56

 

[Don't Tread On Me]

Right, I understand that part. Everything tumbles in a tissue medium, but for the sake of the discussion, it's safe to regard very late tumbling as no tumbling at all. Any round that begins to tumble at or after the point of exit isn't effective as to what we're discussing. What I was wondering is if there is a performance-based velocity threshold on the 5.45.

Let's say you dermine that a 545 or 75gr .223 needs to tumble within a certain amount of inches after impact. Say, you want it to be 90 degrees turned no later than 4" upon entry (just an example)...does velocity effect how quickly this will happen? Is there a threshold at the top or bottom of the velocity spectrum where this effect changes and thus negatively effects performance of the yaw? Will it not yaw at all under 2,300fps? By not yawing, I mean, in the way it was meant to yaw to produce massive tissue damage (all bullets yaw regardless of speed)

I'm assuming that neither the 545 or 75gr .223 can fragment, they are each hollow nosed, and have solid-non fragmenting jackets.


MTmilitiaman's idea is that the 5.45 has an advantage over the .223 in that it doesn't need the > 2,700fps factor for fragmentation. If you get nailed by a 5.45 at 500 yards and its only doing 1,800fps or something, that the simple design of the long bullet with airpocket nose will still create a significant yaw effect. I'm wondering if that is the case or not.

 

[Bartholomew Roberts]

MTmilitiaman's idea is that the 5.45 has an advantage over the .223 in that it doesn't need the > 2,700fps factor for fragmentation. If you get nailed by a 5.45 at 500 yards and its only doing 1,800fps or something, that the simple design of the long bullet with airpocket nose will still create a significant yaw effect. I'm wondering if that is the case or not.

My thinking would be that 5.56x45 still yaws even at 1,800fps since it is still tail heavy and more rounded, much slower rounds like 9mm will yaw inside a human body. I also imagine it would make a bigger hole in yawing since it is both wider and longer than 5.45x39, though I am pretty skeptical the small difference would amount to any practical benefit.

 

[MTMilitiaman]

Hmm. I guess I really don't care. I'll stick to 7.62x39 and let everyone else get all giggly about the .22 centerfires.