How Deadly Is 5.56 At Close Range?
BY Herschel Smith
1 month, 2 weeks ago
This is certainly something we’ve seen before, but I’m always down for another gel test with 5.56.
And here’s another reason a change of the main battle rifle for the U.S. military was stupid. But I’ve told you that before.
On December 10, 2025 at 1:09 am, RHT447 said:
5.56–Proving once again that the only thing is has going for it is velocity. No mention of barrel twist rate. I would assume 1:7 for all. Would be nice to run the same test at 300 yards. Stack the gel blocks for bigger target.
On December 10, 2025 at 11:11 am, george 1 said:
In other words if you wanted something practical with more power you could have just gone to the AR10 with it’s 308 cartridge and accomplished 90 percent of what you hope to accomplish with the .277 fury. You would spend far less money with no over pressure issues.
On December 10, 2025 at 11:54 am, Georgiaboy61 said:
If one looks at the mid-1950s requirement for the Army’s light automatic rifle the proposal specifies a lightweight, .22-caliber weapon which is select-fire and has wounding characteristics similar to the .30-caliber carbine within its range envelope of 0-300m.
These are the performance marks that Eugene Stoner and his team at Armalite had to meet.
Since the caliber of the weapon was specified, Stoner et al. did not have the option of increasing the bore diameter to improve terminal effectiveness. Stoner then looked at the characteristics of light-weight high-velocity projectiles, specifically that they displayed dynamic instability at high velocity. In other words, the propensity to tumble upon encountering a barrier or target. Or what is termed the “fleet yaw effect.”
By designing the 55-grain FMJ bullet w/ cannelure to shatter or fracture at high impact velocities, they were able to generate multiple wound channels, rather than a single one. Out of a 20-inch barrel M193 did 3240 fps, a MV which allowed the bullet to shatter at most normal combat ranges, thereby enhancing its effectiveness.
However, given the necessity of high impact velocity for optimum performance of M193, if the bullet encountered a target beyond its fragmentation threshold range, its terminal performance was reduced and a caliber-sized hole often resulted with no further effects.
This dichotomy accounts for the inconsistencies and disparities in performance of the original generation of M-16s and M193 ammunition. The entire system was dependent upon high MV for its effect on target, that, and the slug fragmenting as it penetrated that target.
In sum, then, the M-16 assault rifle’s performance is highly dependent upon ammunition choice and subsequent ammunition performance.
These observations were confirmed by SOF-Delta Force operators during the Battle of the Black Sea, in 1993, where these elite soldiers were able to observe multiple center-mass hits at close range from M855 62-grain “green tip” ammo (the round which replaced M193 in 1985 as the NATO standard), which failed to bring down enemy militiamen.
These and other incidents started the ball rolling by the late 1990s on R&D to improve the ammunition for, and thereby the lethality of, the M-16/M-4 family of weapons. These efforts have borne considerable fruit, which is one reason why this family of weapons has persisted in service for so long.
Specifically, BTHP bullets heavy for caliber have been discovered to be extremely effective out of an AR platform, in particular 77-grain OTM designs.
Also, barrier blind bonded solids have been highly-effective against sheet metal, automotive glass, and other artificial barriers.
Finally, despite some drawbacks such as accelerated feed-ramp and barrel wear, the new M855A1 has been effective as well.
On December 10, 2025 at 12:06 pm, Herschel Smith said:
@george 1,
Or maybe just stick with what they had since it was fine.
On December 10, 2025 at 3:23 pm, Georgiaboy61 said:
The “fleet yaw” effect also does much to explain the contradictory reports of hyper-effectiveness and under-performance of 5.56 M193 rounds in Vietnam. For many years, military authorities struggled to reconcile the conflicting after-action reports from that time, both sets of which seemed to be genuine and truthful insofar as their writer’s impressions were concerned. There really were inconsistencies in the performance of the cartridge and the weapon. How to explain them?
It took considerable technical research and some years for the fleet yaw explanation to be arrived upon, but it has been confirmed using ultra-high-speed photography and other methods and is now more-or-less settled science.
Rifle projectiles obey the same physical laws as other bodies spinning at very high RPMs. Like a spinning top which wobbles and rotates eccentrically at first, but settles down – “sorting itself out” in the vernacular – rifle bullets exhibit similar behavior. The bullet rotates eccentrically around its long axis at first, its tip inscribing a steep-sided narrow cone – but as it settles down, it assumes a greater consistency.
A second given data point is that spitzer (pointed) bullets are generally light in the nose, heavy in the rear, which means the center of gravity is aft. What keeps the slug pointed in the right direction is its high rate of rotation around its long axis – which is the same as the bore axis.
Any such bullet, if it slows enough, or if it encounters a barrier, will want to “swap ends,” i.e., orient itself heaviest portion forward.
These two effects drive the performance of M193 – or fail to drive it.
A bullet traveling at or above the threshold for shattering, and which exhibits yaw, will likely perform as intended by attempting to swap ends and breaking into multiple fragments.
One traveling at below the threshold and/or which has settled down too much to exhibit fleet yaw, will likely not shatter and will tend to under-perform in terms of terminal ballistics. It may even just punch a caliber-sized hole in the target without inflicting any other damage.
In 1985, NATO agreed to a new bullet design, the 62-grain “enhanced penetration” round, known as the “green tip” or SS109/M855. It’s wounding effects were intended to be equivalent or better than 55-gr. M193, but its LR penetration better against such things as an enemy (Warsaw Pact) helmet, which is what M855 was designed to pierce at 500m.
In reality, M855 only confounded the issue to a greater extent. Since it was designed to penetrate deeply, its propensity for “ice-picking” through targets instead of fragmenting properly quickly became evident during operational use. As at the Battle of the Black Sea in Mogadishu, Somalia, in fall 1993.
These developments, as previously noted, have driven a great deal of ammunition R&D since the 1990s inside the military establishment, such as at the Crane Center for Naval Special Warfare, Crane, Indiana, and by the various establishments of Army Special Forces, to name a few.
But to return to the original Vietnam-era problem of conflicting after-action reports on the performance of the M-16/M-4 family of weapons and their ammunition, the findings on fleet yaw seem to confirm that both data sets are valid. The rifle and its cartridge performed very well under some circumstances and for some users, but inconsistently or even poorly for other users.
On December 10, 2025 at 7:40 pm, RHT447 said:
Some interesting history.
https://jouster2.com/Sagaof16Part1.html
On December 10, 2025 at 11:44 pm, Michael Gilson said:
I’m reminded of Ian’s video about the experimental Spanish 7.92 cartridge. A very light bullet but very long and low drag, made from copper jacketed aluminum. So how about a 5.56 bullet of the same length and profile as the 77 grain ultra low drag bullet, but only weighing 55 grains?
On December 11, 2025 at 2:21 am, Georgiaboy61 said:
@RHT447
Defense Secretary Robert McNamara is the “heavy” or villain in this story, if you ask me. He’s the guy who ultimately decided that it was A-OK to switch service rifles in the middle of an ongoing “hot” war, and who compounded the error again by pulling the plug on the M-14’s production, and yet again by committing the “black rifle” to combat before it was ready for prime time.
Whether you love or hate or are indifferent to the M-14, by 1963 it was coming out of factories in decent numbers and the teething problems which always seem to follow new-production weapons had largely been ironed out. The rifles worked and most of the men issued with them liked them and found them to be reliable, rugged, accurate and hard-hitting.
Was it ideal for use in Vietnam? Opinions vary – but the fact that it was available and had been properly sorted out counted for a lot. Bear in mind that most of the guys who went over there early on had trained with either an M-1 or an M-14 (the two are quite similar so transitioning from the M-1 to the M-14 would have been fairly simple).
Almost none had even seen an M-16, let alone trained with one or had any time to learn it thoroughly.
Handing those guys new rifles on the eve of their going into the bush was not only criminally-stupid, but irresponsible and negligent. McNamara’s arrogance got a lot of good men killed.
The bottom line is that there was no pressing or compelling reason to make that kind of switch during the middle of the war.
Of course, the fiasco of the weapon’s initial use in SE Asia eventually leaked out back Stateside, and Congress held the Ichord Hearings in 1967, which finally forced the Pentagon and the service chiefs to take the problems seriously. McNamara should have been fired – or worse – for his role in the whole fiasco but of course, he wasn’t.
On December 11, 2025 at 2:06 pm, RHT447 said:
@Georgiaboy61 at 2:21 am.
Agree 100%. Will set aside McNamara rant for now. As for the rifles, as you say, opinions vary. Many are the stories of those who made the transition and then asked for their M-14’s back. Had they been issued the M-16 and ammo as we know it today, maybe not so much.
I am well familiar with the M-1, M14, and M-16. Graduated Small Arms Repair School at Aberdeen Proving Grounds in 1974 where I first learned my way around the innards of the M-14 and M-16. Bought my (first) M-1 through (then) DCM in 1983 ($121.96!). As a civilian, shot all three in service rifle matches. Still have most of my “stash” of stuff, including a spare M-14/M1A bolt that I packed in my gear, just in case. I think I paid $35 for it at a gun show long ago. It is complete, new, TRW.
One of my M1A’s I bought from the estate of a late shootin’ buddy. I’m pretty sure I am owner #3. The heel of the receiver reads:
A.R. Sales Co.
So. El Monte. CA.
Mark IV Cal. 308
Very early M1A. They produced less than 200 rifles. According to Lee Emerson, named the Mark IV because the company owner was a fan of the Lincoln Mark IV auto.
On December 11, 2025 at 10:56 pm, Georgiaboy61 said:
@RHT447
Re: “Bought my (first) M-1 through (then) DCM in 1983 ($121.96!). As a civilian, shot all three in service rifle matches. Still have most of my “stash” of stuff, including a spare M-14/M1A bolt that I packed in my gear, just in case. I think I paid $35 for it at a gun show long ago. It is complete, new, TRW.”
You lucky dog, you! Those were the days, right??
BTW, you were smart to learn about small arms on Uncle Sam’s dime. That’s the way to do it.
Re: “A.R. Sales Co. So. El Monte. CA. Mark IV Cal. 308”
Supposedly all of the early M1As were made using USGI surplus parts, to the extent possible – meaning except the select-fire bits. They were highly-desired rifles for that reason. Lots of forged – not cast – components, everything done to spec. No cutting corners.
If I recall my history correctly, SA was started by the Reese family circa ~ 1975 or so, right?
I’ve never owned an LRB or a Fulton, but understand that they are extremely well-made.
On December 12, 2025 at 12:32 am, RHT447 said:
@Georgiaboy61 at 10:56 pm.
Re: “Those were the days, right??”
And how. Cue Edith and Archie Bunker.
As to M-14/M1A history try here (free download)–
https://www.milsurps.com/content.php?r=315-M14-Rifle-History-and-Development-(by-Lee-Emerson)
On December 12, 2025 at 11:19 am, george 1 said:
@ Herschel @ Georgia Boy 61,
Also the 20″ M-16, as designed by Stoner, is much more lethal that the M-4. The M-16 is also lighter and handier that the M-7. If you put a suppressor on it, then it becomes a little much but you have the M4 if a suppressor is needed.
On December 12, 2025 at 3:23 pm, Georgiaboy61 said:
@ george 1
Yep, that’s right: Stoner designed his weapon around a twenty-inch tube and using M193 55-grain .224-caliber ammunition designed especially for the project.
As time passed, into the 1980s and 1990s, and barrel lengths shortened for specialist purposes, such as CQB weapons, it was found that the original forms of ammunition for the M-16/M-4 did not produce satisfactory results, i.e., M193 and M855.
In particular through short-barreled weapons firing subsonic ammunition. Quite obviously, a 55-gr. slug moving at subsonic velocity is little different than a shot from a .22 rim-fire… and most people would agree that is simply not enough power for military use.
These outcomes ultimately resulted in a considerable effort to develop newer and more-modern forms of ammunition which would perform well out of these short-barreled and often suppressed weapons, such as 300 AAC/Blackout, 6.8 SPC, the various OTM designs, etc.
The 300 BO round works great from a short barrel, suppressed or not, and is adaptable to subsonic or supersonic use. Versatile cartridge.
On December 14, 2025 at 5:24 pm, Bones said:
Anthony Huber and Joseph Rosenbaum are unavailable to comment.