M193 in the leg.

[strambo]

Fascinating thread, I'm glad it Zombie'd back since I missed it the 1st time!

[win&legend]

Better late than never lol. But seriously, one of the studies even referenced called out the pronounced early yaw of 5.45 and the fact that it produced a significant permanent wound cavity. Fragmentation is not a reliable method of wounding at longer ranges as the velocity loss due to fluid resistance (in this case, air) ensures inadequate velocity upon impact to beak apart the projectile, thus another method was needed for military general purpose penetrator cartridges. The Russian's figured out the only method which isn't highly velocity dependent back in the 1970's. The US finally caught on with M855A1, if it doesn't fragment, it will still yaw due to it's long body and concentration of weight to the rear, hence it's much more effective at longer ranges where M855 and M193 have a significant loss of wounding potential (MK318 is highly effective at range on soft tissue being a heavy HP). Either that or use more traditional methods like hollow points in the aforementioned MK318, however they are still somewhat velocity dependent (but to a much lesser degree). Unfortunately for the military, hollow points don't fit the bill for a general purpose penetrator (all around cartridge) cartridge requirements however, but MK318 does do pretty well against common barriers like automotive glass, multiple layers of drywall, cinder blocks etc...it's just expensive being of match grade quality.

Page 33 of ADA183285 is what I'm referencing: "The bullet typically yaws at a shallower penetration depth than other military bullets. This results in a significant wound even in uncomplicated extremity hits."

[Molon]

. . . but MK318 does do pretty well against common barriers like automotive glass, multiple layers of drywall, cinder blocks etc...it's just expensive being of match grade quality.

MK318 is hardly "match grade quality."



Accuracy Evaluation of MK318 Mod 0

An accuracy (technically, precision) evaluation of the MK318 Mod 0 ammunition was performed following my usual protocol. This accuracy evaluation used statistically significant shot-group sizes and every single shot in a fired group was included in the measurements. There was absolutely no use of any Group Reduction Techniques (e.g. fliers, target movement, Butterfly Shots).

The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for. Also, a "control group" was fired from each barrel used in the evaluation using match-grade, hand-loaded ammunition; in order to demonstrate the capability of the barrel. Pictures of shot-groups are posted for documentation.

All shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The barrels used in the evaluation were free-floated. The free-float handguards of the rifles rested in a Sinclair Windage Benchrest, while the stock of the rifles rested in a Protektor bunny-ear rear bag. Sighting was accomplished via a Leupold VARI-X III set at 25X magnification and adjusted to be parallax-free at 100 yards. A mirage shade was attached to the objective-bell of the scope. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below.




The Wind Probe.




In order to establish a working baseline for the intrinsic accuracy of the 62 grain SOST projectile itself, when fired from a semi-automatic AR-15, I worked-up a SAAMI pressure hand-load with pulled MK318 bullets and fired a 10-shot group of that load from a Krieger barreled AR-15 from a distance of 100 yards. The Krieger barrel has a 1:7.7” twist rate.




Prior to firing the 62 grain SOST hand-load, I fired a 10-shot control group consisting of hand-loaded 62 grain Berger hollow points. The extreme spread for the control group measured 0.66”.






The extreme spread of the 10-shot group of the 62 grain SOST hand-load measured 1.9”.











Since MK318 Mod 0 is intended for use as a combat round, I used AR-15s with chrome-lined, NATO chambered barrels for this accuracy evaluation, as it most likely that these are the types of barrels that this ammunition will most commonly be fired from. It is possible to obtain better accuracy from mil-spec/NATO pressure loads by firing them from an AR-15 that has a stainless steel match-grade barrel with a hybrid chamber such as the Noveske NMmod0 chamber or the Wylde chamber for examples; but you're not going to make a silk purse out of a sow’s ear.

As previously mentioned, it is reported that MK318 was “optimized” for a 14 inch barrel, so it seemed only fitting to evaluate MK318 from a similar length barrel. The first test vehicle used in this accuracy evaluation was a 14.5” Colt M4A1 barrel. The barrel was free-floated with a Daniel Defense Omega rail. (I was not able to use the mirage-shade with this barrel, due to the original standard front sight base on it.) A previous accuracy evaluation of this M4A1 barrel demonstrated that this barrel is capable of excellent accuracy for a chrome-lined, NATO chambered barrel. That evaluation can be viewed here:

https://www.m4carbine.net/showthread.php?t=59364








A control group fired from the M4A1 barrel using hand-loaded 62 grain Berger hollow-point projectiles had an extreme spread of 1.13”.





Three 10-shot groups of the MK318 were fired from the Colt M4A1 barrel from the previously described bench-rest set-up. The extreme spreads of those groups measured:

2.91”
3.22”
2.70”

for a 10-shot group average extreme spread of 2.94”. The three 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius of this composite group was 1.02”.


The smallest 10-shot group of MK318 fired from the Colt M4A1 barrel is shown below.






The next test vehicle was a 16” Colt HBAR with a 1:9” twist. This is the same barrel found on the Colt 6721 Tactical Carbine. This barrel is one of the most accurate “out of the box” chrome-lined, NATO chambered barrels that I’ve evaluated. The barrel was free-floated with a LaRue Tactical handguard.






A 10-shot group from this barrel fired using hand-loaded Sierra 52 grain MatchKings had an extreme spread of 0.98”.





Three 10-shot groups of the MK318 fired from the Colt 6721 barrel produced the following extreme spreads:

2.98”
2.85”
2.89”

for a 10-shot group average extreme spread of 2.91”. These three groups were also over-layed on each other to produce a 30-shot composite group with a mean radius of 0.82”.


The smallest 10-shot group of MK318 fired from the Colt 6721 barrel . . .






The third barrel used to evaluate the accuracy of MK318 was a 20” Colt HBAR with a 1:7” twist, chrome-lining and a NATO chamber. The barrel is free-floated with a PRI handguard.





A 10-shot group from this barrel fired using hand-loaded 55 grain Sierra BlitzKings had an extreme spread of 1.18”.





Three 10-shot groups of the MK318 fired from the 20” HBAR had extreme spreads of:

2.70”
2.49”
3.24”

for a 10-shot group average extreme spread of 2.81”. As before, the three 10-shot groups were over-layed on each other to form a 30-shot composite group that produced a mean radius of 0.91”.


The smallest 10-shot group of MK318 fired from the 20” HBAR . . .





A summary of the results from this evaluation are shown below.







....




Lastly, for the Internet Commandos in our viewing audience, here’s a pic of a sub-MOA group of the MK318 fired from the 16” Colt HBAR from 100 yards; a cherry-picked 3-shot group that is.





.....

[MegademiC]

Molon, the depth, detail, and completeness of your posts is much appreciated. As a young engineer, I try to apply these aspects to my reports, and it's gaining me respect quickly. I just want you to know your impact extends beyond the forum.

Thank you

Btw, what I find most incredible is how it seems you have HOURSSSS of research data on hand at a moments notice.

[win&legend]

According to an international ballistics report in which MK318 was referenced as a supposedly sub MOA cartridge (which was my source on this issue), but it was NATO source, so perhaps they mixed up MK318 with another military cartridge (MK 262?). The data speaks for itself, as an Engineer myself (electrical), I can't argue with the literal results. It would seem the real intent of MK318 is primarily better common barrier penetration and wounding at longer ranges over that of M855, given it's much higher mass (conservation of energy) and traditional expansive wounding mechanism, being a hollow point.

[Molon]

Molon, the depth, detail, and completeness of your posts is much appreciated. As a young engineer, I try to apply these aspects to my reports, and it's gaining me respect quickly. I just want you to know your impact extends beyond the forum.

Thank you

Btw, what I find most incredible is how it seems you have HOURSSSS of research data on hand at a moments notice.

Da nada.


...

[Molon]

According to an international ballistics report in which MK318 was referenced as a supposedly sub MOA cartridge . . .

Dude, just stop already. Try getting some actual experience on a subject matter before posting any more false information in our technical forums.


....

[win&legend]

Molon, I'm not arguing with your results on MK318. You cherry picked a part of my reply without reading the context...the reason I thought MK318 was supposed to be a match cartridge was because of that international small arms report I referenced previously in which there were addressing the lethality and accuracy issues of M855. That's all that was meant, no need to be a smarty pants, I'm sure you've made mistakes as well ;-). Regardless, MK318 was intended to fill a role M855 and M193 could not, and that was at longer ranges, match grade or not.