DD MK12 SPR 5.56 NATO 77 gr. SMK QL/Node/OBT Help

[longrangehunter]

Oh I'll get the P35 out! I never like going into something blind like I did yesterday, and why measuring case head expansion doesn't work IMO! Those were all within every 223 case I've ever measured and yet the last one @ 20.6 was way too hot! Punched the plunger well into the case head and had some powder burn 1/3 the way around the primer! No-No-No!

I wouldn't have worried had the data come from a manual, but that powder was too fast and not used by anyone in that bullet weight. I should have known better but the QL program lured me into a false sense of security, and no, I'm not blaming it or you for it. Which is why a chronograph is so important, although even then knowing the amount of gain/loss due to barrel length still needs to be addressed, as well as the small variances in powders lot to lot.

I'll think of that one round as a proof round test, I'm sure DD builds them to endure a round cooking in the chamber at over 250* degrees and then being fired after a long battle. But I'm not about to keep testing without the chronograph getting into unknown territory again.

Thanks Dewey.

 

[longrangehunter]

Got snow late yesterday, 3"-4", which has now turned to rain as of this morning, that sucks! I live in the far North for the snow, the rain just turns the ski runs into concrete when it refreezes. Not good for the Wildlife either, tough to dig through rock hard snow to get at the forage. Doesn't look like I'll be able to get out the chronograph out in this rain.

Who said anything about singing in the rain? I'd prefer snow!

 

[longrangehunter]

Did some testing using the P35 this morning, interesting. So the Data I'm listing below is well over published data in just about every manual out there, SO PLEASE DO NOT USE MY DATA IN YOUR WEAPON/OR RIFLE W/O WORKING UP!!

I looked at the three/four manuals that list NATO rounds in an AR and from the barrel length I determined the speeds I was getting to be within the expected velocity range. Most manuals say roughly 24 FPS per inch of barrel length difference. Berger uses a 24" barrel, Sierra a 20" barrel, Hornady 20" barrel, Nosler uses a 20" barrel all using RL-15 but in different cases and primers used, as well as the gun used.

RL-15; CCI-41; FC 12 223 Rem Brass @ 2.262" coal.

23.0 2330-01-2329
24.0 2452-02-2450
25.0 2622-03-2620
25.5 2662-04-2659
25.5 2652-05-2647

ALL @ 20' from the muzzle.

Both Nosler and Sierra listed 2685/2600 fps as a max with their 77 and 80 grain bullets, this is w/a 20" bbl. and both in a 1:7" Twist which is what I'm using. There for I will use that as my baseline and since I have 2" less in barrel length I will call that near max, and drop down to the 25.0 range since that seemed to have less a difference between the two screens.

25.5/5 shot averaged
2656 fps@20" muzzle
H 2688
L 2638
ES 50
SD 21

Too much ES and SD for me. I will post the 25.O data later. Oh, the groups were ok, and not worth posting. Within MOA I'd say.

 

[Dwh7271]

I'll adjust one for what you actually got.

 

[Dwh7271]

Kevin,
I adjusted this one for what you actually got. Your case capacity, speed, and barrel.

Cartridge          : .223 Rem.
Bullet             : .224, 77, Sierra HPBT MatchK 9377G
Useable Case Capaci: 26.523 grain H2O = 1.722 cm³
Cartridge O.A.L. L6: 2.262 inch = 57.45 mm
Barrel Length      : 18.0 inch = 457.2 mm
Powder             : Alliant Reloder-15 ?

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step    Fill. Charge   Vel.  Energy   Pmax   Pmuz  Prop.Burnt B_Time
 %       %    Grains   fps   ft.lbs    psi    psi      %        ms

-10.0   94    22.95   2376     965   37337   9193     86.5    1.146
-09.0   95    23.21   2404     988   38600   9331     87.2    1.128
-08.0   96    23.46   2432    1012   39903   9467     87.8    1.111
-07.0   97    23.72   2461    1035   41246   9601     88.5    1.094
-06.0   98    23.97   2489    1060   42630   9734     89.1    1.077
-05.0   99    24.23   2518    1084   44058   9864     89.7    1.061
-04.0  100    24.48   2547    1109   45537   9992     90.3    1.045
-03.0  101    24.74   2576    1134   47068  10119     90.9    1.029
-02.0  102    24.99   2605    1160   48654  10242     91.4    1.013
-01.0  103    25.25   2634    1186   50297  10363     92.0    0.998
+00.0  104    25.50   2663    1212   52001  10482     92.5    0.982
+01.0  105    25.76   2692    1239   53766  10598     93.0    0.968  ! Near Maximum !
+02.0  106    26.01   2721    1266   55597  10711     93.5    0.953  ! Near Maximum !
+03.0  107    26.27   2750    1293   57496  10821     94.0    0.938  ! Near Maximum !
+04.0  108    26.52   2779    1321   59466  10927     94.5    0.924  ! Near Maximum !
+05.0  110    26.78   2808    1349   61511  11030     94.9    0.910  ! Near Maximum !

Results caused by ± 5% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 5% relative to nominal value:
+Ba    104    25.50   2746    1289   57297  10686     95.6    0.941  ! Near Maximum !
Data for burning rate decreased by 5% relative to nominal value:
-Ba    104    25.50   2570    1129   46822  10161     88.5    1.029

Look s like 25.4 and 23.97 are spots for you.

 

[longrangehunter]

Thanks Dewey, I didn't see your post until after these two (5) round groups were tested, but this is what I settled on for today for the best accuracy I could muster out of the DD MK12 w/a USO 1-8x27 scope w/a custom BDC reticle for the 77 gr. SMK although calibrated supposedly to 2750 fps, I'll just have to wait an see?

I tested 25.0 and didn't like what the chronograph was telling me, too high ES, and SD's. This group is at 3 o'clock of center.

25.0 RL-15
Avg. 2608 fps @ 20'
ES 69
SD 28
H 2645
L 2576

So I went with 25.2/25.3, yes to see if it happened to do nothing with the speeds, which tells me that's the sweet spot. Which IMO it was, but not really a better group, this is the one closest to center at about 1 o'clock. The closest to center low was 24.0, the other is the 25.2/.3.

25.2/25.3 RL-15 CCI-41 FC 12 223 Rem Brass @2.262"

H 2638
L 2609
Avg 2625 @ 20'
ES 29
SD 10

The upper right groupings are from the (1) @ 25.0, (2) @ 25.5 and another (5) @ 25.5, not 100% sure, but 20 rounds were fired which mean 2 were close to 2 others just not sure in what order? Nothing to fancy about the groups IMO, but then it is an AR.

 

[Dwh7271]

That'll work.
Let me know if you'd like anything else.

 

[longrangehunter]

Thanks again Dewey.

At this point I think I'll need to change the primer, I've heard a lot of other people like the Wolf SRM primer in the 5.56 NATO. With this powder, I think I'm close? The gun only has 30 round through it, so I think it should only get better from here, we'll see.

The snow has started to come down and I didn't get any more testing done. But with this it's at least a start.

 

[Dwh7271]

That might do the trick. Good idea.

 

[Wyo7200]

Skimming through this venture, noticed you asked about the bolt not holding open- sounds like you were over gassed with that load. Heavier buffer, stronger spring or go for it all and get a silent capture spring from jp enterprise. Even if it's cycling with the 25.3g load, I'd recommend it.

Something else to consider, I shoot groups of 6 in my ar's because either the first or last (or both) round will be a flyer a lot of the time. Not sure if it's the reduced friction on the bcg from no bullet causing it to drop pressure faster or something else with the movement. I've had ar's group well though so may or may not be your case.


Good luck

 

[Alaska]

MK 12 mod 0 load


TAC at 24.8 (my favorite is 24.0)
WW brass
WSR primer
77gr SMK
COAL: 2.245" (MK 262 Mod 1 Standard)

My MK 12 Mod 0 has .102" gas port size with standard rifle length gas tube on 18" Douglas Barrel is Crane Spec.
I use a M16 Auto carrier for additional weight along with H Buffer or standard A2 buffer in fixed stock

Some shooters have problems with being overgassed because their gas port size is too small which effect the cycle rate to be to fast.....bolt bounce also.

A slow bolt is a happy bolt in the AR

 

[longrangehunter]

The Daniel Defense MK12 uses a gas block to Crane's specifications made from a solid piece of 416 stainless steel, and produces them under contract for SOCOM. The gas port is the standard .099 size though, it uses a rifle length gas system and an H buffer in a carbine length receiver tube. DD MK12 uses a chrome lined M16 bolt carrier, along with a Geissele SSA trigger.

I'm thinking of replacing the stock with either the standard A2 receiver extension and the standard A2 stock or a Magpul PSR stock? I have a LMT DMR stock that will go on a carbine length tube extension, I'm just not sure which way I want the end product to turn out that is the most efficient and useful?

Magpul's UBR stock is another option I was contemplating using simply because it still makes the stock collapsable, and leave a solid check rest w/o any play in it.

 

[Alaska]

Crane that built the MK 12 used .102" on the port size , but .099 is very close. They used the .102" gas port size so it would cycle with the Ops Inc CAN on and off.
On the Mod 0 like mine used a PRI front sight/gas block.
The Mod 1 had a Badger low profile gas block that I beleve is no longer made but copied by others.

Vltor A5 EMOD system stock and A5 buffer system would work excellent with the 7 position stock

DD is best known for their contributions to the MK 18 forearm they changed it from knight to DD.

Good choice on trigger......the MK 12 at first had a Knight 2 Stage trigger after a AD in a veh they switched all Knights to the SSA-E trigger

The man (Alan Brown) that engineered the MK 12 retired from Crane and started his own company

http://highcalibersales.com

 

[longrangehunter]

The rifle I bought is not a true copy of the MK12 Mod 0, 1, SPR/A, SPR/B or the H "Holland" that were used for combat. Instead Daniel Defense's idea of what they came up with, and the Geissele came standard on this rifle from them.

I looked into making a clone of the MK12 Mod 1, but the parts are hard to come by and some of them are very expensive, like the KAC front (P/N 99051) and rear (98474) back up sights for instance, that's $500.00! I just couldn't see spending all that coin when even the Troy back-up sights are still expensive, and you either build it like the original(s), or why attempt to in the first place?

This was shot yesterday off the bi-pod prone in the snow at 179 yards, (unknown distance at the time). Not bad, the first few, (3) I wasn't sure were they went but the barrel had been cleaned and not fouled out. Then I noticed a hit on the steel T post which helped with the POA.

 

[longrangehunter]

For those interested here's a very well written list for the various MK12's.

The following parts lists and substitution parts was compiled by lancecriminal86 over the course of a LOT of research. Read up and pay attention!

Below are the 100% .mil-spec parts lists to build a true SPR or Mk12 clone. Some of these parts are no longer manufactured and will require much effort and money to locate through forums and online brokers. Keep in mind the rifles were built off donor M16A1s, hence the prevalent A1 parts in the lower receivers and the BCGs. They were also first configured using parts available from 1998-2004, and most are inferior in some ways to newer designs. If this bothers you too much, STOP NOW.

The rifles were issued as a kit in a Pelican 1700 case with cutouts. The kits included the rifle with suppressor, optic, bipod, an Eagle TAS-1 UMSS sling (unobtanium and also absolute crap), with a Dewey 1-piece cleaning rod plus Otis cleaning kit, and a cutout for magazines. An operator’s manual was also included, however these have not been officially released for public consumption. However, the manuals are out there, and some companies building Mk12 uppers include one. Whether these are official .mil operator's manuals or specially made is currently unclear as the manual itself still contains language that it is not for distribution.

- Alternate .mil-spec parts due to NFA, NLA parts, or changes in name/markings for current production in [brackets]

- Extra notes about parts or availability are in (parenthesis)

LOWER
Lower receivers were standard across the SPR/Mk12 variants and the only variations would be between grips, stocks, and buffers. Most were marked either Colt or GM Hydramatic. All other parts were the same in regards to the lower parts. One caveat is the trigger, as the program originally selected the Knight’s Armament 2-stage Full Auto Match trigger. Later on, some issues regarding negligent discharges occurred, and Geissele SSF triggers ultimately found their way into the Mk12 family. Whether 100% of all Mk12s eventually received the Geissele trigger isn’t clear, so either is acceptable.

Lower: M16A1 pattern [Nodak Spud NDSA1 or 80% re-profiled/finished/engraved]
Trigger: Knight’s 2-Stage Full Auto Match Trigger or Geissele SSF [KAC semi-auto Match or Geissele SSA/SSA-E]
Grip: A1, A2, ERGO Original
Stock: Originally issued with A1 stocks, both solid D and trapdoor E types; as A1 stocks dwindled, A2 were used; ModH rifles rebuilt with Ace SOCOM stocks
Small parts: Standard M16A1 parts
UPPER
The upper receivers, which ultimately differentiate the four variants of the Mk12, have the most variation between each other.



Early SPR/Mod0
Upper: Colt, Diemaco, or Armalite marked, flat top, M4 feed-ramps
Barrel: Douglas 416r SS, 18” SPR contour, 1/7 twist, flats milled for PRi FSB (Compass Lake, Centurion Arms, High Caliber Sales, and PRi can all supply barrels that meet the appropriate spec minus FSB flats)
BCG: Colt M-16
Handguard: Precision Reflex Gen I carbon fiber free-float Handguard, rifle length (identified by button-head screws and one vent hole near barrel nut on lower half; no heat shields)
A.R.M.S. #38 SPR MOD Sleeve (either the PEQ version or with uneven spacing on the front ¼ but not the full 1913 railed version)
FSB: PRi early folding front sight base and gas manifold, set-screw, with elevation wheel
Charging handle: PRi Gas Buster M-84 with military latch
Muzzle device: OPS Inc 12th Model brake/collar, and 12th Model suppressor [Allen Engineering AEM5 and brake/collar]
Rear iron sight: A.R.M.S. #40
Scope rings: A.R.M.S. #22 Medium rings, #22 Tactical Ring Cap and #22 Tactical Ring Rail (rings should not include "lever-stop” hump as produced later by A.R.M.S.)
Optic: Leupold Vari-X III 3.5-10x40mm LR, M3 turrets, illuminated Mil-Dot reticle (use .308 turret) [Leupold LR/T 3.5-10x40 LR, M3 turrets, Illuminated Mil-Dot reticle]
Bipod: Versa-Pod with A.R.M.S. #42, or a Harris with A.R.M.S. #32 (Versa-Pod far inferior to Harris)



Late Mod0
Upper: Colt or Diemaco marked, flat top, M4 feed-ramps
Barrel: Douglas 416r SS, 18” SPR contour, 1/7 twist, flats milled for PRi FSB (Compass Lake, Centurion Arms, High Caliber Sales, and PRi can all supply barrels that meet the appropriate spec minus FSB flats)
BCG: Colt M-16.
Handguard: Precision Reflex Gen III carbon fiber free-float handguard, rifle length
A.R.M.S. #38 SPR-PEQ-2-3 Sleeve
FSB: PRi folding FSB, set-screw, .750 (original production had PRi’s full address engraved on sight tower; those engraved with "PRi USA” are later manufacture)
Charging handle: PRi Gas Buster M-84 with military latch
Muzzle device: OPS Inc. 12th Model brake/collar, and 12th Model suppressor [Allen Engineering AEM5 and brake/collar]
Rear iron sight: A.R.M.S. #40
Scope Rings: A.R.M.S. #22 Medium rings (rings should not include "lever-stop” hump as produced later by A.R.M.S.)
Optic: Leupold 3-9x36mm TS-30, Mk4 MR/T 2.5-8x36mm TS-30A2, M2 turrets with Mk262 BDC, illuminated TMR reticle
Bipod: Harris with either A.R.M.S. #32 or KAC RAS bipod adapter


SPR/A, SPR/B, Mod1
Upper: Colt or Diemaco marked, flat top, M4 feed-ramps
Barrel: Douglas 416r SS, 18” SPR contour, 1/7 twist, flats milled for PRi FSB (Compass Lake, Centurion Arms, High Caliber Sales, and PRi can all supply barrels that meet the appropriate spec minus FSB flats)
BCG: Colt M-16
Handguard: Knight’s Armament M4 Match FF RAS, rifle length (now called the SR15/16 Match FF RAS)
Gas block: NSWC Crane pattern (Badger Ordnance parkerized/NSN version is correct, has open front of gas tube hole)
Charging handle: PRi Gas Buster M-84 with military latch
Muzzle device: OPS Inc. 12th Model brake/collar, and 12th Model suppressor [Allen Engineering AEM5 and brake/collar]
Scope rings: A.R.M.S. #22 High rings (A.R.M.S. rings should not include "lever-stop” hump as produced later by A.R.M.S.)
Optic: Leupold Mk4 MR/T 2.5-8x36mm TS-30A2, M2 turrets with Mk262 BDC, illuminated TMR reticle or NightForce 2.5-10x24 (optionally with NightForce rings)
Bipod: Harris with KAC RAS bipod adapter (BRM-S, A.R.M.S. #32 could still optionally be used)


ModH, Mod "Holland"
Upper: Colt or Diemaco marked, flat top, M4 feed-ramps
Barrel: Noveske 16” Recon, mid-length gas system, profiled for OPS Inc. 12th Model brake/collar (will require aftermarket contouring of most barrels)
BCG: Colt M-16
Handguard: Precision Reflex Gen III carbon fiber free-float handguard, FDE, rifle length
Charging handle: PRi Gas Buster M-84 with military latch
Muzzle Device: OPS. Inc. 12th Model brake/collar, and 12th Model suppressor [Allen Engineering AEM5 and brake/collar]
Scope Rings: A.R.M.S. #22 Medium rings on PRi recce rail (rings should not include "lever-stop” hump as produced later by A.R.M.S.) or LaRue LT-104 SPR mount
Optic: Leupold 3-9x36mm TS-30, Mk4 MR/T 2.5-8x36mm TS-30A2, M2 turrets with Mk262 BDC, illuminated TMR reticle, Leupold Vari-X III 3.5-10x40mm LR, M3 turrets, illuminated Mil-Dot reticle (use .308 turret) [Leupold LR/T 3.5-10x40mm LR, M3 turrets, illuminated Mil-Dot reticle]; S&B Short-Dot
Bipod: Harris with either A.R.M.S. #32 or KAC RAS bipod adapter
Iron sights: (apparently PRI were supplied but never used)


In the Wild

Naturally, once these rifles were issued to units, operators and even Marines used various non-issued parts. Here is a short summary of what has been seen:

Early SPR/Mod0 - Both Leupold 3.5-10x40mm and 3-9x36mm scopes have been used. Many have had carbine stocks like the old CAR-style, enhanced M4, SOPMOD Gen I, or even the Tactical DuoStock swapped on.

Mod1 - One 3rd SFG-issued rifle pictured with SSgt Robert J. Miller (MoH recipient) used an A.R.M.S #36 S-EX 5.56mm rail, and a Leupold M3X 10x fixed-power scope, possibly pulled from an M-24 or SR-25 rifle. Another has been seen with a Magpul PRS, LaRue mount, and a Premier Reticles 3-15x used by an AMU shooter, and a similar rifle was pictured on a FOB in a very posed-looking photo. Further, a USMC-issued Mod1 was seen using #22 Medium rings instead of High rings, and a LaRue mount has been spotted as well. Grips have varied from the usual A1, A2, and ERGO, and at least one Magpul MIAD has been used. As with the Mod0s, carbine stocks like the SOPMOD and M4 have been used on Mod1s.

ModH - The Mod "Holland" was already a small-batch configuration, but even as soon as they were issued to 5th SFG units, some Ace SOCOM stocks were replaced with Magpul ACS and CTR stocks. Optics are basically anything existing in the unit's inventory, from S&B ShortDots still in the system, the 3-9x and 3.5-10x Leupold scopes from earlier Mod0s, and there’s even a photo of an ELCAN on a Mod1 floating around. No non-magnified optics like EOTechs or regular Aimpoint M2/M4s, but Micros have been seen on offset mounts. Backup iron sights, as a whole, were almost entirely left unmounted. Grips were again the same usual selection.



Parts Alternatives for Clone Building

Many parts are rare, expensive, and/or both. Despite this, there are some alternatives to a 100% pure clone that will still provide the same visual look and performance. While not a museum-grade clone, most would be hard-pressed to discern the difference. Just know there are those of us out there that will haze and peer-pressure you into further moving your build towards a true clone.

Barrel - Popular options are the White Oak Armament SPR barrel (rifle gas), BCM’s SPR barrel, Rainier’s Match and Ultramatch offerings (ensure it’s the SPR contour with 12th Model profile), Ballistic Advantage’s SPR barrel. Compass Lake Engineering can also spin a Mk12 profiled barrel with a Criterion chrome-lined blank, or even a Krieger, which was one of the original contenders for the program. The DPMS Mk12 barrels are NOT properly profiled for a clone.

Optics & Rings - In the case of the Leupold 3-9x or 3.5-10x, it’s generally okay to go for a non-illuminated version of either, sometimes with M1 or other turrets and reticles. As far as the NightForce scope, the 2.5-10x24mm is not generally released to the public anymore (with one recent exception through Sniper’s Hide), so many use the 32mm or even 42mm versions with the #22 High rings. As for the rings, any of the recent produced A.R.M.S. #22s with the lever-stop humps are functionally the same, the desire for non-lever-stops is purely aesthetic when going for the most authentic look. As LaRue LT-104s have been seen in use, it is justifiable to use one depending on whether you have a specific rifle you want to copy, or even just if you absolutely cannot acquire #22 High rings.

A.R.M.S. #38 SWAN Sleeve - The #38 family of sleeves are no longer available. Finding them secondhand usually cost $250-$300 easy, more for rarer early variants. Fortunately, PRi’s copies of the sleeves look and function almost identically, with minor visual differences. PRi and other builders supply these currently for complete Mod0 builds.

FSB - While the set-screw version of PRi’s FSB is spec, most use the cross-bolt, clamp-style version. They are extremely robust, and when aligned and torqued, have been shown to hold strong enough that you’ll probably shear your barrel extension pin or upper before it budges. This is mainly how Mod0 uppers are supplied by most vendors, including PRi themselves.

Suppressor, Brake/Collar - Diverging from the OPS Inc. or AEM brake and collar will get you MAJOR flak. Trust me, I’ve been running an AAC SPR/M4 for years now and it took a LONG time to not get clubbed every time I posted it. The Allen Engineering AEM5 is basically the current production of the OPS Inc. 12th Model, as they were originally made by Ron Allen and his team in the first place. Only minor differences separate original OPS Inc. cans from AE cans, and these are only obvious to trained eyes.

As far as the rest, you can swap Colt parts out for any other .mil-spec parts, like BCM, DD, CMT, etc. Any billet uppers/lowers, funky BCG coatings, extended bolt releases, etc. are extremely frowned upon. Remember, once you start going down the path of building a "better” rifle rather than what was spec, you’re quickly beyond clone territory and would have been better off building a custom 16” or 20” rifle. Cloning is generally viewed as all-in or not at all.

[/u]

 

[Alaska]

That is a good right up ....I built my Colt using that blueprint.......even got the Douglas MK 12 barrel and leupold TS 30A2 scope
It took me 3 years to get all the correct parts......mil spec covers a wide range ......I noticed a lot of quality issues from manufactory to manufactory. Great quality med quality to poor quality.

Completed 2013 and even have the TM manual.

I have used several stock configuration A2 , LMT sopmod .......but the one I like the best is the Vltor A5 extension with the Vltor EMOD stock......get the best of both rifle length buffer spring an 7 position extension very nice.

 

[longrangehunter]

Jeff,

Had I known about Allen Brown and the Company he formed, High Caliber Sales, I would have gone to him for a complete upper receiver build! That is the right stuff and all done by the very person responsible for producing them correctly in their various configurations.

At the time, I was rushed into grabbing another AR due to the incident down in CA, and an upcoming Match. It's not like I hadn't know about the evolution of the MK12's, it was more of putting together the various parts and having it all done correctly.

Kevin and Allen seem to have put together a great company for these type of rifles, and one I would be proud to own. Had I not just bought the one I own, I'd be calling them up tomorrow!

Thanks for the info, if I ever sell my 35 Whelen I'll ask Allen to build me one of his MK12 mod 1's.

 

[longrangehunter]

I had put together another 60 pieces together yesterday, and just went out to test (10) on the 8" round steel from the same position as the last time only I changed the seating depth to what Jeff had listed the MK262 coal at: 2.245" (5) and another (5) at 2.250" coal.

I had known the Black Hills Ammo was load to what I had written down as 1.869" CBTO, but odd I can't find my comparator for .224 cal. so I used Jeff's COAL he listed for the 77 gr. OTM. What stuck out in my mind was the moniker "262" and why not use that name based on the COAL of 2.262"? I haven't read anything on where the name came from and why, but that had stuck out in my mind although I had read the load wasn't loaded to that length.

Anyways, both seemed to produce good combat groups at 179 yards on the steel. I tried to use a fixed aiming point and account for the bullet drop in the reticle which allowed me to center punch the steel. Hard to tell which OAL was better between the three different loads on the steel target, and off a bi-pod, but very capable for a battle gun IMO when they are all landing near center of the 8" steel.

It would had been better to pull out the chronograph, but the sun is out and the snow is falling off all the trees. I place the P35 directly under a huge Cedar tree which would have ended in disaster? The change in Velocity and ES, numbers would have been beneficial, but in this case, it's just as capable without that information for putting rounds on target w/o missing, which is good enough for the chicks I run with! lol

 

[Alaska]

Blacks hills loaded it at the length to prevent bullet run out.......and to operate freely in different M16 magazines from different manufactures

Coal 2.245" for Mk262 mod 1 from black hills

 

[longrangehunter]

Made a typo error on the COAL info above Jeff, typing too fast and not thinking the numbers correctly. I'd like to retest them off a bench, but I don't think at 100 yards the bullets have fully stabilized? Which from my home I either use the bench at 100 yards or field positions out to 600 yards.