Do 5.56 fmj often break up when they hit flesh or water?

I don't know if those properties were reduced so much as altered to be closer to what other larger, heavier slugs do. Still yaw and tip just not doing it until after exiting the body.

Flesh is not uniform, impact angles are not uniform, bullets always get some degree of upset from impact and passing through flesh. Tumbling while still inside a body makes bigger wounds. Tumbling after exit happens but has no effect on the wound size.
 
No ... from experience ... shooting water jugs .
5.56 fmj ( Full Metal Jacket ) do not break up . The full jacket holds the lead core in place and they do not mushroom or break into pieces .
We had a lot of military surplus ammo that was cheap and we would shoot the ammo at water jugs , sand banks , boxes of water soaked newspaper...just to see what it would do and for the empty brass for reloading .
Gary
 
Don’t know if by “break up,” the OP meant the well-noted “yaw” effect that occurs when a 5.56mm FMJ penetrates into a fluidous mass at full velocity, but the splitting apart (or “breaking up”) of a portion of the 5.56 projectile is a documented fact.

Lotsa dead southeast asian enemy soldiers learned that back in the 1960s and early 1970s. My Uncle Jimmy, from back in the ‘Nam, used to tell me about the mess it made of a human torso. :eek:
 
Recommend you visit the www.jouster2.comwebsite...

the originator was the Late Major Culver, USMC ret'd.

Who education was a Ballistic engineer during his career with the Corp.,

he wrote about his observations during the introduction of the M16 during the VN event.

There are good reports that need to brought to light.
 
22 cal twist rates were 1-12" or 1-14".
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I don't think there is any "or" to it.
The standard twist for the .222 and .222 Magnum is 14".
It sticks in my head that they made some ARs at 14" but went to 12" to stabilize a boattail bullet in cold dense air.
 
Twist rate does have a factor in this discussion, as does impact velocity.

Way over stabilized, or unstable, hitting at high speed, yep, it is going to come apart most likely. Stable, hitting at low speed, it is most likely not going to come apart. It's a dance of the two factors, as well as the specific bullet design.

There are definate differences in gelatin and Fackler box testing where the only thing changed was the spin rate. Same with only changing the impact velocity.

The devastation with the new 8.6 Blackout (1:3 twist) pretty much makes it a solid only proposition for good terminal performance. Bullets that work well on Elk, Moose and Bear from bolt guns with 1:10 to 1:12 twists are flat out exploding on impact from the 8.6 Blackout.
 
Per Speer #11 (1987)

.222 Rem
1-14" 8 rile makers
1-16" 1 maker

.222 Rem Mag
1-12" 1 maker
1-14" 4 makers

.223 Rem
1-10" 1 maker
1-12" 5 makers
1-14" 2 makers

so, I would say that while there are common twist rates, there was no standard twist rate and each rifle maker used what they thought best.

Also remember this was back when the heaviest civilian or military bullets in common use were 62-63gr.
 
I think 1-12 or 1-14 marginally stabilize 62gr bullet. With slight perturbation it will tumble.

-TL

Sent from my SM-N960U using Tapatalk
 
No idea. This info is for entertainment only - no underlying messages here:

In "The Gun", researched and written by a former (US) Marine infantry officer, he describes that the DoD in the early 60's acquired some Human Heads to compare damage by 5.56 with 7.62x39 bullets.
Many of you know about the book.

Iirc, he stated that the DoD kept the results of the test classified.
Mybe this isn't connected to the OP's question, but I found various segments of the book interesting. Secondary sidenote: Chivers is a prize-winning writer for the NYT.

https://www.amazon.com/Gun-C-J-Chivers/dp/0743271734
 
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Just FYI, I have a Win M70 in .22-250, with a 1-14" twist. That rifle shoots 55gr just under an inch, 52/53gr match/varmint bullets into 3/4" or sometimes a bit better, and the 63gr Sierra "semi spitzer" into about 2"-2.5" groups.

Since that Sierra bullet is the "deer bullet" of its era, and I got some in a trade, I did test some to see how they did. Adequate groups for deer but no where near the rifle's potential with varmint bullets.

Since no .22 CF is legal for deer where I live, I've never used those slugs on deer, and have no plans to.
 
With your 22-250, two factors at play
1) Velocity. Ultimately, the twist gets you RPM . RPM gets you gyro stability.
More velocity serves much like tighter twist. For a heavier bullet,a .222 will need a tighter twist than a 22-250.

Nearly all 22 centerfires were developed for light bullets a screaming high velocities, Over Mach 3 sells. 12 or 14 twist and 40 gr bullets,

2) Twist is really about bullet length,rather than weight, A VLD boat tail will require tighter twist than a flat base semi-spitzer.
(FWIW, this somewhat explains the 257 Roberts 117 round nose factory load,)
 
I am the OP. Sorry for the long absence. I knew the answer to my question before I asked it. I’ve read paper from a US Army surgeon that detailed how a 556 fragments. He first observed this while patching up friendly fire patient. He later performed detailed testing on his own and recorded the evidence.

I have also seen it happen with my own two eyes. We 5 gallon water jugs with a 556 with a 10 acre pond behin the jugs . The bullet penetrates the water jug, and then there are multiple splashes in the pond behind it. Not skips in a line but erratic splashes. Anwy it’s interesting to me. I assume it’s a way for the USmilitaryto skirt around the rules of war.

I’m not here to toot my horn. I’m just genuinely shocked that so few people who should be knowledgeable don’t seem to know anything about this.

I appreciate the respectful, although sometimes inaccurate responses on this forum.

However, it was very interesting to me to see angry, insulting responses on another social media site about the same subject.

It’s not too often, and Old well-informed gun enthusiast learns something new so this is one of those times.
 
The father of one of my supervisors taught firearms training at Lackland AFB in the 60’s. My boss told stories of shooting water filled ammo cans with the 55gr FMJ to show its performance. He said quite often the cans would be filled with flecks and larger pieces of bullet material.
Obviously a metal can is different from a human target but it wasn’t simply two .22 diameter holes by any means.
My cousin’s son shot a wild turkey through the bread basket at about with a 16” AR using 55 gr FMJ. It totally destroyed the poor bird, totally pissed me off too.
It was nothing but wings and drumsticks, very explosive.
I doubt if the bird offered enough resistance to cause the bullet to come apart but bullet rpm, velocity and or unstableness after impact sure messed things up.
 
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Before providing an explanation of the JSWB IPT’s results, a brief discussion of small caliber, high velocity terminal ballistics is in order
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Upon impacting the target, the bullet penetrates tissue and begins to slow. Some distance into the target, the tissue acting on the bullet also causes the bullet to rotate erratically or yaw; the location and amount of yaw depend upon speed of the bullet at impact, angle of impact, and density of the tissue. If the bullet is moving fast enough, it may also begin to break up, with pieces spreading away from the main path of the bullet to damage other tissue.
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The yaw of the bullet increases the damage and ideally that yaw will occur in the target. That yaw can cause fragmentation but that is not consistent enough to be a purposeful act of design. The yaw is the purposeful and principle wounding pathology of the round.

Field reports are accurate and can be explained by the phenomenon of bullet yaw.
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Unfortunately, projectiles impacting at different yaw angles can have significantly different performance, particularly as the projectile slows down. Consider the two photos on this page. In the first (Figure 6), the bullet impacted at almost zero yaw. It penetrated deeply into the gel block before becoming unstable. In a human target, it is very likely that this round would go straight through without disruption – just as our troops have witnessed in the field.
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https://apps.dtic.mil/sti/tr/pdf/ADA519801.pdf

What does that mean for a civilian AR15 in home defense? Barrel Length and ammunition matter....

The most yaw performance variation in the 5.56mm NATO round is in the first few feet at Close Quarter Battle Distances. The Shorter the barrel, the greater the chance the bullet will not yaw upon impact at CQB distances.

A 16 inch barrel is longer than any of the SOCOM rifles used by those making the reports about a lack of lethality. The army standard 55 grain FMJ round was the one being used. Going to a heavier grain weight bullet eliminated the issue in a SBR.
77 grain delivered consistent results at CQB distances.

If you are going to use an AR15 to defend your home then pick one that is not a SBR and pick the heaviest weight bullet you can find in order to realize the yaw characteristics that are important to the stopping power of the cartridge.
 
I’ve found that FMJ in the caliber mentioned is unpredictable when hitting meat-based organisms.
On the other hand, something that is intended to fragment in light fast calibers, such as Varmint grenades will expand with devastating results at close range.

With .223/5.56 it’s the velocity that does the work.
 
If you are going to use an AR15 to defend your home then pick one that is not a SBR and pick the heaviest weight bullet you can find in order to realize the yaw characteristics that are important to the stopping power of the cartridge.
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Or, simply do not use military ammunition unless you are required to, by law.
 
About 15 years ago, I would kill trapped pigs using a variety of calibers and bullet construction as impromptu experiments. This included 5.56 NATO and .223 hunting bullets. I shot several hundred pigs in this manner. The walking ballistic dummies were there and available, so why not try out different stuff.

The 5.56 NATO definitely killed them but the wound profiles varied from the “ice pick” type wounds that davidsog has mentioned in the past, to extremely gruesome. There were some exits as well.
With .223 hunting ammunition, most were instant incapacitation and I found the lighter fragmenting ammunition to be the most effective at short range.
If I had no choice for defense ammunition except 5.56 NATO fmj then I would use it without hesitation, but there’s way way better alternatives on store shelves.

Edit to add: This is not considering and type of body armor involved
 
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