Ballistic gelatin test results : M-855 62gr FMJ

[Brass Fetcher]

Cartridge : 62gr M-855 FMJ

Firearm : 5.56x45mm rifle with 14.5" barrel length and 1/9 inch twist

Block calibration : 12.9cm at 590 ft/sec

Single shot fired to the center of the block from 10' distance. Bullet impacted at 2923 ft/sec and penetrated to 14.1". Bullet penetrated point-forward until 1.9" penetration depth, at which time the bullet yawed. The bullet entered the non-cavitating flow regime at 10.3" depth. Maximum permanent cavity had a diameter of 5.5".

One 7.2gr piece of lead was recovered from the penetration track at 5.9" depth. The bullet evidently maintained some semblance of core-jacket integrity, as only minor copper and lead fragments were recovered from the rest of the penetration track.

 

[Glock19Fan]

Hello!

Its been a while since I have been on this board, or even communicated with you! Not sure if you remember me, but you have come a LONG way since last time I remember.

Anyway, just curious, but did the bullet stop at 14.1 inches, or did it exit the block at that point?

In my own testing of the M855 (but from a 16 inch 1:9 barrel), the bullet had a much longer neck, IIRC 6 inches or so, but like you seen, had a relativly large permanant cavity. The bullet had torn just below the cannelure, and what little did fragment separated into roughly 10-12 pieces. The intact, top end of the bullet was not squashed, like the M193 that I have tested in the past.

It seems like a pretty good load when it works, but the problems that I see with it are the inconsistant performance.

 

[Brass Fetcher]

G19 - Of course I remember you...! How are you doing? ... Yeah, I've been doing a few gelatin tests in the past months ... Are you now testing ballistic gelatin? The bullet exited actually at 13.9" - I think that it hitting the table that the block was set upon caused it to fragment - sending a fragment to ~ 14.1".

I had a chance to compare my results with those of the M-855 wound profile put out by Dr. Fackler... I see lots of similarities to that diagram. I was just checking to see if we were 'ballpark' with the results and it looks like the results are... just less fragmentation.

 

[Glock19Fan]

Im doing pretty good, and hope the same for you!

But like I mentioned, these bullets, most likely becuase of the placement of the steel core, are fairly inconsistant in their performance. IIRC, Facklers testing showed a neck similar to what I found. In your test the bullet seemed to yaw a bit quicker than normal, but from what you described, im not sure whether or not this led to more or less fragmentation, although more would be expected becuase a quicker yaw means a higher velocity the bullet is traveling when it turns 90 degrees. Also, I think that much of Facklers 5.56mm testing is done using a 20 inch barrel, which would also give the bullet a higher velocity and more fragmentation, but im not 100 percent sure on which barrel length he used.

I am doing my own ballistic gelatin testing, but not nearly on a scale as large as you are, and it is mostly for personal use, although I will be more than happy to share my results with anyone that is curious.

 

[PercyShelley]

Ouch.

Would blood vessels and other important things have any chance of survival in the wound cavity, e.g. from the little shards of metal being relatively small and destabilized, or would all tissue in the area of the wound cavity just be... um... hamburgered?

 

[Thin Black Line]

JE223, thanks again for another test. Can you "pen" around the cavity to
make it easier to see?

 

[Onmilo]

I have to ask,,,,,,,
What do you have against Gelatin????????

 

[Brass Fetcher]

@PercyShelley - I'm still working on that question myself... From what I understand, the cracking in gelatin that you see far to the sides of the actual bullet is a 'function' of the size of the temporary cavity - in that, the larger the crack size, the larger the temporary cavity was (but the relationship is not a 'direct' relationship so nothing can be easily inferred from the crack size IIRC). If you ever watch a block getting shot (taking your eyes out of focus so you can concentrate on seeing the motion of the block as it is hit), you can sometimes see the temporary cavity of the bullet. This is evident on my video of the .50BMG A-Max test - look close and the block appears to blow out at the sides and top.... but the sides were not torn out on the block ... even though the TC appeared to exceed 14" in diameter (on a 10" wide block).

But it's generally accepted that at velocities greater than 2000 ft/sec, the velocity of a bullet is great enough to push the tissue out of the way faster than it can 'get out of the way of itself', so increased damage occurs. This is why rifle bullets are so much more effective than pistols, although they are lighter and have a smaller diameter. So, short story long... ... for rifles, I just assume that the area destroyed is equal to the area of the front of the bullet (which is conservative for the higher velocity region, but assumes too much damage for the slower speeds where the track looks like a .45ACP made it - so it all should even out decently).

 

[Thin Black Line]

excellent.....

 

[PercyShelley]

But it's generally accepted that at velocities greater than 2000 ft/sec, the velocity of a bullet is great enough to push the tissue out of the way faster than it can 'get out of the way of itself', so increased damage occurs. This is why rifle bullets are so much more effective than pistols, although they are lighter and have a smaller diameter. So, short story long... ... for rifles, I just assume that the area destroyed is equal to the area of the front of the bullet (which is conservative for the higher velocity region, but assumes too much damage for the slower speeds where the track looks like a .45ACP made it - so it all should even out decently).

Thank you for the information. Terminal ballistics interests me, probably because I have a vested interest in never getting shot.

Fantastic work all around.

 

[RockyMtnTactical]

That specific testing you did showed less fragmentation, but you should realize that sometimes bullets fragment, sometimes they don't. There's a lot that goes into it.

Fragmentation is a great way to add to the overall damage done by each hit... but shot placement is far more relevant when it comes to effectiveness of the round.

At any rate, cool test. I'm not trying to ridicule your results or anything. I think it's probably a fairly accurate portrayal of the performance of the M855 round. It's on the lower end of the more effective 5.56 rounds, but it can still be quite devastating.

In reference to the effectiveness of the 62gr M855, one of our troops who served in Iraq commented, “One guy who was hit by a short barreled M249 at between 100-150m had 10 entry wounds and 14 exit wounds.”

According to that experience that was related to me, some of the rounds fragmented and even split into two seperate halves... most didn't.