Terminal Ballistics From Lucky Gunner
BY Herschel Smith
1 year, 3 months ago
The only thing I’ll say is that I’ve seen M193 perform an awful lot better than that. Something was wrong with that test and I don’t think it’s indicative of what .223/5.56 can do.
On August 31, 2023 at 4:26 am, Ratus said:
Yea, that M193 test seems to be an outlier result.
On August 31, 2023 at 2:18 pm, foot in the forest said:
Lips and Hips
On September 1, 2023 at 12:31 am, Georgiaboy61 said:
Overall, a worthwhile lecture IMHO…
However, the presenter is not entirely correct when discussing kinetic energy. He implies that kinetic energy alone is not enough to make a high-velocity projectile effective. This is clearly false, and later in the presentation – perhaps inadvertently – he proves it by showing the dramatic performance of the Barnes 150-grain .308 caliber load as compared to the earlier examples in .224-caliber.
Consider an extreme or exaggerated example: A battlefield combatant unfortunate-enough to get in the way of a 750-grain FMJ/Ball .50-caliber BMG projectile moving at 2820 fps will literally be obliterated if the hit is at all center-mass. Why? Because that round possesses so much kinetic energy (13241 ft-lbs) that it literally overwhelms the ability of the tissues of the human body to remain joined together by the normal means -whether chemical, physical or biological.
Remember, too, that if the projectile is still spinning at anything like high revolutions-per-minute, the force applied isn’t simply going to be linear along the axis of the projectile path, but rotational – as that massive torque is applied to the tissues of the target.
Kinetic energy is extremely important to terminal ballistic performance. It is simply that when dealing with ordinary small arms fire – handgun and small-bore rifle cartridges (most militaries define ‘small-bore’ as being .30-caliber or less), the effects are not as pronounced as with larger, heavier ordnance and are therefore not always easily calculated or their effects readily observed.
Companies which make hunting, anti-personnel (self-defense) and similar loads for small-arms generally consider three main axes when designing a projectile and a performance envelope for it: Penetration, expansion, and muzzle velocity.
By international agreement, many nations abide by rules prohibiting expanding or hollow-point bullets in small-arms ammunition, but over the years, R&D has uncovered a variety of work-arounds which allow militaries to abide by the letter of the law if not always the spirit.
Regarding the performance of 55-grain M193 Ball/FMJ, the presenter did not provide much information about the manufacturer, date/time of manufacture, and other variables. If we assume that the round was produced according to NATO specs, that narrows the field somewhat, but still leaves some things open to question. How long was the cartridge in storage before being fired? What firearm was used to fire it, with what length and twist rate of barrel? Did it meet the velocity spec originally set forth by the STANAG aggreement? And so on…
As far back as Vietnam, the operational performance of M193 Ball was inconsistent and tough-to-pin down when doing after-action reports, intelligence estimates and the like. Soldiers and Marines reported occasions when the new M-16 and its ammunition provided devastatingly-effective results against enemy personnel, but other reports provided conflicting information suggesting dissatisfaction with the performance of the new cartridge as fired from the new weapon.
These inconsistencies in data were not pinned down entirely during the war and it was some years later before ballistics and other authorities understood the mechanisms involved in the performance (or lack of same) by M193 and the M-16 itself.
Back in the mid-1950s, when Armalite chief engineer Eugene Stoner was working on the army’s high-velocity light rifle project, he was faced with a series of design goals specified by CONARC, the army command which had issued the RFP. First, the weapon had to be chambered in .22-caliber. Second, it had to be capable of select-fire operation. Third, the weapon had to have wounding potential equivalent to or greater than the old M-1/M-2 Carbine and its 110-grain .30 Carbine round, out to 300 yards or so (which was the maximum effective range of that weapon and cartridge).
Normally, meeting these requirements would not have been a problem, except for the fact that the caliber was already set at .22-cal. and to an extent the bullet weight, too, since the relatively small case limited how large and heavy the projectile could be while still meeting the army’s high-velocity requirement.
Stoner looked closely at established data on small-caliber projectiles fired at high velocities, and he noticed that this class of bullets was marked by relative dynamic instability in gyroscopic terms, which is to say in terms of their rotational stability along the axis of flight. In plain language, a lighter and shorter bullet fired at a given high velocity would tend to become unstable sooner than a heavier, longer one would at the same MV.
Today, we know this phenomenon as the “fleet yaw” characteristic of the M193 round, and the degree to which the slug exhibits this yaw is correlated highly with its terminal ballistic performance.
As Stoner and his team designed the M193 full-metal jacket projectile, it was of standard lead core and gilding metal jacket construction, but it possessed a crimping groove or cannelure, which was by then more-or-less standard on military ball ammo (to improve reliability and lessen the potential for bullet set-up during magazine feeding and chambering).
At impact velocities of ~ 2500 fps or more when fired from a 20-inch 1:14 RHT barrel, the M193 bullet was designed (intended) to fragment when encountering living tissue, thereby creating not only a single high-velocity permanent wound track, but multiple ones – thereby increasing its wounding potential and lethality. However, hidden in that model was the fact that Stoner et al. needed the proper amount of fleet yaw in the projectile’s flight for it to perform as intended.
If the bullet was over-stabilized (too gyroscopically stable) and did not exhibit sufficient yaw, it would tend to “ice pick” or simply produce a caliber-sized hole in the target without fragmentation. If, on the other hand, the bullet did yaw properly and possessed sufficient MV to fragment as intended, the wounding effects could be dramatic indeed.
Stoner’s original AR15 which became the M-16 service rifle was equipped with a 20-inch barrel in recognition of the fact that the longer barrel helped the cartridge attain its MV potential and full performance in the field. Moreover, the original rifles had 1:14 RHT barrels, which is a rate of twist commonly found in varmint rifles which fire lightweight bullets. Relatively quickly, however, cold weather tests seemed to show that the new rifle’s twist was not adequate for low temperature performance, so the rate was made faster at 1:12 going forward… which is the twist rate of the M-16s used in Vietnam.
Today, with barrels being shortened to carbine length (14.5-16 inches), or even SBR-pistol length (as short as 10.5 inches) and with much faster rates of twist on many barrels, such as 1:7, it is easy to grasp why M193 “still” does not perform predictably under all circumstances. The same has also been true of its replacement in military use, SS109/M855 62-grain ball/FMJ.
It is entirely understandable that M193 Ball/FMJ does not perform as Stoner intended, when so many changes have been made to the original system he designed, from the formulation of the propellants used in the cartridge, to barrel length and rate of twist, and much else besides.
In tactical terms, if the user wants to get as close as possible to Stoner’s original performance obtained with the old M193 Ball/FMJ cartridge, then use a rifle as close to those original specs as possible. Why? Because that’s how the man designed the system to work. In other words, a 55-gr. full-metal jacketed lead-core slug moving at about 3240 fps as fired from a 20-inch barrel with a 1:12 rate of twist.
According to the data I have seen, Stoner’s original design was intended to be especially effective out to 150-200 yards, which is about right for an assault rifle’s performance. The rifle was still lethal out to 500-600 meters/yards, but not hyper-lethal as within typical close to medium ranges encountered most often in combat.
If you crop the barrel to 14-5-16″ your hyper-lethality (assured fragmentation) zone drops to about 75-100 meters/yards and in, and so on as barrels get even shorter.
If you want to run a shorter barrel, in particular one shorter than carbine length, you will be best-served by using a more modern ammunition design, something intended from the start to work from a shorter barrel with a faster twist. This is in fact what the professionals have done, such as the elite members of such units as the army’s SOF-Delta, Marine Raiders, Navy SEALS, and U.S. Army Special Forces, to name a few.
On September 1, 2023 at 11:36 pm, Dirk said:
I started stacking ammo back in the early 80s. I’ve many many many cases of 556 55 g, 62 g, Past few years 77 g mostly, I’ve noticed a trend over the years, while I try and shoot up the older stuff first, ammo constructions come along ways. The metals, the primers the-powders, the bullet constructions just better.
I would support the observation that somethings not right with that testing.
A month ago maybe two I opened a wooden AK bullet box and discovered a full unopened case of 9mm Silver tips bullets. I had to smile. Talk about a walk down memory lane.
Recall when silver tips were all the rage! Thank good I was shooting a Colt model70 with 230flying ash trays. I don’t think the 1911 10 rounds mags were out just yet. I went to them as soon as they were battle proven.