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https://youtu.be/fX4ODh1g4eM

I thought it was interesting that, although presumably only one round was fired, it looks like two bullets exiting the gel. I assume that what we are seeing is the entire jacket being shed as one piece, and the core as the "other" bullet. Upset is pretty dramatic, as is the size of the temporary stretch cavity.

There is also an interesting secondary phenomenon of an explosion of gases as the temp cavity collapses inward. The best explanation according to the source is "dieseling". Because the gel material is somewhat flammable, between the unburned gasses of the shot, the vaporized gel due to friction of the bullet passage, and the increase in pressure as the cavity collapses, there is a spontaneous "diesel"-like explosion that takes place, which blows a bunch of smoke back out through the entrance hole. Fascinating video.

That is interesting, especially the "dieseling." I had no idea that would happen.

The Annoyed Man wrote:I thought it was interesting that, although presumably only one round was fired, it looks like two bullets exiting the gel. I assume that what we are seeing is the entire jacket being shed as one piece, and the core as the "other" bullet. Upset is pretty dramatic, as is the size of the temporary stretch cavity.

M855-A1 has no "core". It is an all copper round except for it's large steel penetrator which is exposed at the tip and secured to the rest of the bullet with a cannelure. The bullet is also significantly longer than the M855 projectile.

It's designed to yaw at approximately 3" in. When it does yaw, it will break apart and fragment at the cannelure. Watching the video, it appears the rear portion of the projectile exits the end of the block. Note that both ends appear to be flat. The front (pointy end) looks like it veers off and exits the gel on the near side.

ELB wrote:That is interesting, especially the "dieseling." I had no idea that would happen.

In the TFB post where I found the video, the source was clear to say that it would not happen inside a human body.....that it was most likely a product of the flammability of the gel.

Here's the original link: http://www.thefirearmblog.com/blog/2015 ... round-gel/

M855 on the left, M855A1 on the right:


A significant difference in bullet construction. On the original, the steel penetrator sits on top of a lead slug, and both are swaged into a fully enclosing copper jacket (except at the base). With the A1 version, there is no lead (which was one of the major reasons for developing the bullet was the political pull for an "environmentally friendly" bullet), as Pawpaw has pointed out. Instead, we have a protruding penetrating "dart", semi-wrapped in a solid copper slug. It looks like it was actually designed to come apart, and not just from bullet yaw. My guess is that the two components decelerate at different rates, so even if there was no yaw, there might be a tendency for the penetrator to separate from the copper slug.

Tell you what though......they are proud of that stuff. I just found an ad on Gunbroker where someone is selling 10 rounds.......that's right.... TEN rounds..... with a "buy now" price of $150.00! Fifteen $$ per round for 5.56 ammo? I'll pass. It isn't THAT good.

One of the other main reasons the Army went to this round is because it's barrier blind. By it being two pieces it can still penetrate but will also work better on people. They looked at how the regular M855 was going through people since we are fighting unarmored thin people. The original round was designed for the Cold War. The M855A1 also burns hotter/higher pressure.

On another note the Marine Corps and SOCOM are using open tipped. I forget which is which but they are using Mk 262 and Mk 318. The Marines are using a 62 grain weight and SOCOM are using 77 grain. These are basically Barnes and Black Hills bullets.

http://www.shootingtimes.com/ammo/speci ... -1-review/

http://archive.marinecorpstimes.com/art ... fghanistan

I don't know if the current M855A1 ammo is any better than a few years ago, but G & A doesn't seem to think very much of this round.

http://www.gunsandammo.com/uncategorize ... d-marines/

Among other things, there's this:

This means that not only are parts going to wear out at a much higher rate (which is already is an issue with the M4), but if, God forbid, there is any bullet set-back, the number of M4s reportedly going “high order” (i.e., blowing up) should increase exponentially.

What matters if it can penetrate level 3+ or 4 BA at 300 yrds

Beiruty wrote:What matters if it can penetrate level 3+ or 4 BA at 300 yrds

Well, apparently it can't even penetrate Level 3 at point blank, from either a 16" or 22" barrel:
https://www.youtube.com/watch?v=fQth9vdjINw

For $15.00 each, I want grenades I can launch with an M79 launcher.

Abraham wrote:For $15.00 each, I want grenades I can launch with an M79 launcher.