Ran across this at a local place… haven’t seen any of this is a long time, is it any good?

Disregard.

Mk318 Mod 1
Yes it's good. $600 for 800 rounds is a good price too

Got through reading all the random tidbits that people seem to have posted around the site in the past... seems like a fun round to have and good for home defense. I was using a tungsten round for my HD mag, but it seems to have gone missing during one of my recent moves... too lazy to unpack everything to find them. I'll see if the dude is willing to trade wares, the price is still a bit steep.

Random info and photo dumps:

As an FYI, PSA/AAC mentioned in another thread that they're planning to manufacture MK318 next year.  I don't think it was mentioned if MOD 0 or MOD 1, or if they were sourcing bullets from the OEM or making that in house.

Very good price for the Qty.  I’ve never seen it loose like that. It also is not “match ammo”

I’ve never seen it loose.  For a SBR, it’s a stellar round.

I shot some of my Mod O today. 5 shot groups at 100 yards from bench, sandbag rest: 3.5" and 3.55". I've gotten better groups with it but 3.5" seems about average for me with Mk318.

Mod 0 seem to shoot like that. Mod 1 definitely shoots tighter groups for most people

Mod 1 is definitely tighter shooting.  I’m shooting sub 1” groups at 50 yds. Anything further is not shot for groups- steel and IDPA type targets. Mod 0 definitely shoots bigger groups

MK318 Mod 0 (Federal T556TNB1)







One version of MK318 Mod 0 that is now available to the general public is being sold as Federal "white box" T556TNB1.  The SOST projectile loaded in the MK318 Mod 0 cartridge has a nominal weight of 62 grains and a nominal length of 0.87”.  It is constructed with a copper base and a small, non-bonded lead core in the ogive section of the bullet.  Due to this higher copper to lead ratio, the MK318 Mod 0 projectile is longer than a traditional copper jacketed/lead core projectile of the same weight, but is still slightly shorter than an M855 projectile.










While it is often stated that the SOST projectile used in MK318 Mod 0 is similar to the Federal Trophy Bonded Bear Claw, the form of the SOST projectile more closely resembles that of Federal’s Trophy Bonded Tip projectile (without the tip of course.)  As previously mentioned, the MK318 projectile does not have a bonded core.

















The loaded MK318 Mod 0 cartridge has a nominal OAL of 2.20". The projectile does not have a cannelure per se, but the case mouth is crimped into the top relief band.  The cartridge is sealed at the case mouth, however not with the asphalt sealant typically found on military ammunition.  The primers are sealed and crimped.  The casehead is stamped "FC 10".  The cartridge is charged with ball powder.








A typical copper jacketed/lead core FMJ bullet will have a specific gravity of approximately 10.2.  Due to its higher copper to lead ratio construction, the MK318 Mod 0 projectile has a lower specific gravity.  When fired from  typical AR-15 barrel lengths with a 1:9” twist rate, MK318 Mod 0 will have a gyroscopic stability factor of  approximately 1.3.






When fired from typical length barrels with a 1:7" twist rate, MK318 Mod O will have a gyroscopic stability factor of approximately 2.2.








MK318 Mod 0 Chronograph Data

Chronographing of the Mk318 Mod 0 ammunition was conducted using an Oehler 35-P chronograph with “proof screen” technology. All velocities listed below are muzzle velocities as calculated from the instrumental velocities using Oehler’s Ballistic Explorer software program. All strings of fire consisted of 10 rounds each.












Each round was single-loaded and cycled into the chamber from a magazine fitted with a single-load follower.  The bolt locked-back after each shot allowing the chamber to cool in between each shot.  This technique was used to mitigate the possible influence of “chamber-soak” on velocity data. Each new shot was fired in a consistent manner after hitting the bolt release.   Atmospheric conditions were monitored and recorded using a Kestrel 4000 Pocket Weather Tracker.






Atmospheric conditions:

Temperature:  75 degrees F.
Humidity:  47%.
Barometric pressure: 29.97 inches of Hg
Elevation:  950 feet above sea level




Two different barrel lengths were used in obtaining velocity data; a 14.5” Colt M4A1 barrel and a 20” Colt M16A2 barrel.  Both barrels have NATO chambers, are chrome lined and have 1:7” twist rates.  Both barrels have low round-counts on them.  


M4A1 barrel.




M16A2 barrel.






For comparison, the MK318 Mod 0 ammunition was fired in sequence with two different brands of 62 grain M855 ammunition.  The firing order for both barrels was as follows:

1.A 10-shot string of Winchester Ranger M855
2.A 10-shot string of MK318 Mod 0
3.A 10-shot string of IMI M855

Finally, the data:










The Crane Warfare Centers' publication, “U.S. Navy Small Arms Ammunition Advancements” reported that MK318 was “optimized” for the MK 16 with a 14 inch barrel and claimed it has a velocity of 2925 fps at 15 feet from the muzzle (presumably from said 14 inch barrel.) The lot of Federal T556TNB1 (MK318 Mod 0) that I chronographed from the Colt 14.5” M4A1 barrel would have a velocity of approximately 2889 fps at 15 feet from the muzzle (at standard atmospheric conditions.)




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 sometimes possible to obtain  slightly 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:

The Colt M4A1 SOCOM Barrel









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”.  (For those of you not familiar with the mean radius, I've posted an explanation of it in the third post of this thread.)


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.








AB49




MK318 Mod 0 is also available to the general public in a “brown box” version.  This version is labeled with the Department of Defense Identification Code of AB49.




- V e l o c i t y  -  C o m p a r i s o n -


Following the same chronographing procedures outlined in the first post of this thread, I compared the velocities of T556TNB1 “white box” MK318, to that of AB49 “brown box” MK318.  The two versions were fired “back to back” from three different barrel lengths:

> 14.5” Colt M4A1 (the same barrel used for the first post)

>  16” Colt light-weight barrel, 6520

>  20” Colt M16A2 (a different barrel than the one used for the first post).


All three barrels are chrome-lined and have NATO chambers and 1:7” twist rates.  The velocities listed below are muzzle velocities as calculated from the instrumental velocities using Oehler’s Ballistic Explorer.


Atmospheric conditions.

Temperature:  72 degrees F
Humidity:  68.1%
Barometric pressure:  30.02 inches of Hg
Elevation:  950 feet above sea level








- A c c u r a c y  -  C o m p a r i s o n -


Using the same 20” Colt HBAR, described in the original accuracy evaluation in this thread, as the test vehicle, I performed an accuracy evaluation of the AB49 “brown box” MK318 ammunition.  The evaluation was conducted from a bench-rest at 100 yards in the same manner as previously described.






Prior to firing the AB49 ammunition, a 10-shot control group of hand-loaded, match-grade 55 grain Sierra BlitzKings was fired from 100 yards.  That group had an extreme spread of 1.00”.








Three 10-shot groups of the AB49 fired from 100 yards had extreme spreads of:

3.26”
3.42”
3.31”

for a 10-shot group average extreme spread of 3.33”.  The mean radius for the 30-shot composite group was 0.98”.  The accuracy results are summarized and compared to those of T556TNB1 below.





The smallest 10-shot group of AB49.





The table below shows an accuracy comparison of MK318 Mod 0 with several other "mil-spec" loads.






.......

Thank you Molon.
The white boxes in your post are the exact same Mod 0 that I have.

Have you had a chance to compare the Mod 0 with the Mod 1? I remember you or someone comparing them but haven't seen the results in a long time.

I have, but I haven't written it up yet.  As others have mentioned, the Mod 1 is more accurate, but terminal ballistics aren't going to be the same because there is no lead core to fragment in the Mod 1.






Mod 0



Mod 1


.....

Great info, thanks. Looking forward to your next post.

If you don't want it I'll pay you $50 to ship to me, and pay you that sticker price.

I have been slowly going through all of my belongings to track down a mag with a certain ammo for a trade. Can't find the damn mag. May have to use money, would be willing to ship some.