cloning MK262 ammo

KimberGuy

KimberGuy

Not a FNG
Full Member
Minuteman
Nov 2, 2007
219
122
Las Vegas, NV
#1
Hey guys, I'm working on building a Mk12 Mod0 clone this winter, and I would like to start loading some ammo for it. I know there are a few Mk12 owners on here, so what are you guys loading up? I don't have any rifle components, so far my reloading experience has been limited to pistol cartridges. So, I will be starting from scratch as far as components and knowledge are concerned. So, what loads are you guys using? My upper will be coming from ADCO, barrel has a twist rate of 1 in 7.

Thanks guys.
 
#2
Re: cloning MK262 ammo

That rifle was designed to shoot Sierra 77gr SMK. You can get them now with cannilure, per mil spec. I believe Black Hills makes the stuff. Not sure what powder/charge weight they use though. I'd probably start with the Sierra reloading manual 10% below max for a powder and work up.

From the Sierra reloading manual:
<span style="text-decoration: underline">Powder</span>
H322--------21.8gr-----2550fps
AA-2230----23.4gr-----2650fps
748----------23.4gr-----2500fps
H335--------22.6gr-----2550fps
TAC---------24.0gr-----2750fps
H4895------23.6gr-----2600fps
XMR-2495--24.1gr-----2600fps
Varget------23.9gr-----2550fps
AA-2520----24.2gr-----2700fps
VV N140----24.5gr-----2650fps
VV N540----24.9gr-----2650fps
RE-15-------24.1gr-----2600fps

<span style="font-weight: bold"><span style="text-decoration: underline">Note: THESE ARE MAX LOADS</span></span> Proceed with caution.

Hope this helps
 
#4
Re: cloning MK262 ammo

Normally, I'd be thinking those propellents area bit fast for the bullet weight, but then I keep coming back to the AR/autoloader issue. It's a bit of a paradox, trying to run heavy bullets in a semiauto, although perhaps less so with the AR.

In a bolt gun, I found that a HDY 75gr HPBT Match (moly) and 26.5gr(C*) of Ramshot Big Game was deadly accurate at 200yd out of a box stock 10FP. I can't really say how that would work in an AR, but I will admit to being quite curious about it.

Greg
 
#6
Re: cloning MK262 ammo

The Sierra data is a bit low and slow.

The Lyman 49th Edition will give you slightly higher powder charges and speeds but not sure it has all the powders you've listed.

Recommendation for loading GI Mark 262 would be to use a match or benchrest-quality neck sizing die (i.e., Forster S-die) and matching that with a high-energetic (like Vihtavuori 540). You won't be able to match velocity.

Black Hills uses a commercial canister-grade powder you won't be able to buy.

Most match shooters will use either Varget or Reloader-15.
 
#7
Re: cloning MK262 ammo

I tried to develop a load similar to Mk262 for my 18" SPR and it was difficult to get one that performed well in the 2700fps range that wasn't too hot. N140 worked best for me.
 
#10
Re: cloning MK262 ammo

David,

Steve and I should be at the TV match the end of Jan. and I could bring mine.

I use LC brass/2.225 OAL/205m/75gr Hornys/25.0gr Varget
This load shoot out of my WOA 18" SPR and also my Noveske 16" REECE
18" SPR shoots aprox. 2715 fps
16" REECE runs aprox. 2630 fps
 
Last edited:
#11
Re: cloning MK262 ammo

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mussman</div><div class="ubbcode-body">David,

Steve and I should be at the TV match the end of Jan. and I could bring mine.

I use LC brass/2.550 OAL/210m/75gr Hornys/25.0gr Varget
This load shoot out of my WOA 18" SPR and also my Noveske 16" REECE
18" SPR shoots aprox. 2715 fps
16" REECE runs aprox. 2630 fps </div></div>

Are you running a midlength or rifle gas system on your 18" WOA? 85fps is a big drop for 2", just curious as I'm gonna be playing with loads for my 18" WOA midgas SPR......sorry to hijack
 
#12
Re: cloning MK262 ammo

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mussman</div><div class="ubbcode-body">David,

Steve and I should be at the TV match the end of Jan. and I could bring mine.

I use LC brass/2.550 OAL/210m/75gr Hornys/25.0gr Varget
This load shoot out of my WOA 18" SPR and also my Noveske 16" REECE
18" SPR shoots aprox. 2715 fps
16" REECE runs aprox. 2630 fps</div></div>

Is that OAL a typo or are you single feeding them?
 
#15
Re: cloning MK262 ammo

Here's My Mk262 Mod 1 clone recipe:

Firearm: Colt LE6921
Barrel Length: 14.5"
Twist: 1:7"
Bullet: Sierra 77 gr BTHP w/cannalure
Brass: Winchester
Trim-To-Length: 1.750"
Primer: Remington 7 1/2
Powder: H335
Charge: 24 gr
COL: 2.260"
Avg Velocity: 2,629 fps
SD: 6.0
ES: 13.13

NOTE: Velocity was recorded 12' from the barrel, temperature 86 degrees, 175' above sea level.
 
#16
Re: cloning MK262 ammo

You mean this stuff?

IMG_1488.jpg
 
#20
Re: cloning MK262 ammo

24 gr Ramshot Tac in LC/ win primer, is realy close, 24.5 would get the velocity but experiencing blown primers. When we first started shooting BH ammo then 262 at the navy matches we pulled a lot and tried to reproduce the load. the closest thing we could get was with the TAC powder. 262 is hotter than 77gr smk over counter, if I can find all of my crono data from several years back will post for issued 262 and TAC data.
 
#23
Re: cloning MK262 ammo

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kyshooter</div><div class="ubbcode-body">Has anyone done an actual side by side comparison of BH 77gr SMK and Mk 262? Am I correct in saying that both are from BH but the Mk 262 is loaded a little hotter. </div></div>

The SAMMI spec for MK262 is NATO spec or .556 spec. BH 77gr is .223 spec and is not as hot. .556 spec is right at the top edge for the case. Black Hills does load both rounds. I found these chrono listing over on Arfcom.

MK262 77gr SMK

20" barrel 2806 fps.
16" barrel 2710 fps.
14.5" barrel 2628 fps.

Hope this is some help.
 
#24
Re: cloning MK262 ammo

V-540 will get you the most velocity with a 77, you just have to watch the pressure. I have ran them to 2850 out of a 1/7 Colt 20". The bolt sheared 2 lugs off after about 2k rounds. I backed it off to 2700 after that.
 
#25
Re: cloning MK262 ammo

I developed my Mk 262 load back about 2004 when I sat and waited 6+ months for the stuff to become available through Georgia?

Rock River TASC rifle, 16", 1:9 twist. Trijicon TA47-2 2x compact ACOG.

LC brass, 2001 and newer
25.5 gr H4895 (thrown, not measured)
older, WSR nickel plated primers
Hornady 75 bthp match.
2.260" OAL

2740 fps 10' from muzzle. 10-shot, 10" group @ 600 yds in 20 deg temps.

Have put over 500 rounds through without a hiccup. Web expansion does not go over .001"
 
#33
Re: cloning MK262 ammo

Out of a 16' RECCE (Noveske polygonal rifled barrel) Chronographed 10' from muzzle with a CED M2.

Avg FPS per 5 shots:
MK262 mod1 (in box).......2732 fps
MK262 (on stripper clips)...2665 fps
24.4gr TAC, LC case, Wolf primer, 77gr SMK...2698 fps (no pressure signs) accuracy on par with factory MK262

That's my limited experience trying to duplicate the MK 262 load with TAC.
 
#36
Re: cloning MK262 ammo

Something has to be taken into account here when trying to duplicate Mk 262 ammo.

1. Pressure is going to be present. Anyone attempting this is going to be dancing on the razor's edge of too much pressure.

PKelly proved that.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: PKelley</div><div class="ubbcode-body">V-540 will get you the most velocity with a 77, you just have to watch the pressure. I have ran them to 2850 out of a 1/7 Colt 20". The bolt sheared 2 lugs off after about 2k rounds. I backed it off to 2700 after that. </div></div>

One may not have a catastrophic failure immediately, but it could happen eventually. I would hope only very experienced reloaders would be the ones to dabble in this arena.

To meet the definition of Mk 262 one does not just use a 75-77 gr bullet That bullet needs to hit or slightly exceed approx 2720 fps from a 16" barrel. The reason being the effective range for the bullet to frag, in the target, is extended from about 50 meter to approx 200+ meters. This is the reason this load is so effective on homo sapiens.

When I developed my Mk 262 load, I tried 1/2 dozen powder and found Varget, H4895 and TAC gave the required velocities with TAC running the fastest. I then compared the 3 for accuracy and "in my rifle" H4895 gave the best. That being 10 shots in 10" @ 600 yds from a bench using a TA47-2 2x ACOG for my optic. This was in 20 deg temps. I tested at that temp because running a 1:9 RRA twist I wanted to make sure the bullet stabilized in the colder air. It worked for me but YMMV.

Alan
 
#37
Re: cloning MK262 ammo


Mk262 Mod 0 Clone Load:
77gr. Sierra Matchking
Winchester Brass (also use WCC +LC cases)
Winchester Primer- WSR
24.-24.5gr. Ramshot TAC
OAL- 2.255" (minor crimp with Lee crimp die)
Velocity- 2,750fps+ from 18" White Oak Armament Barrel

The only thing different from this load an the "real" mk262 ammo is thier powder is a special blend of Ramshot powder. Also their primers are crimped and sealed.
 
#39
Re: cloning MK262 ammo

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: longrange30</div><div class="ubbcode-body">I got 2803fps w/ TAC out of my 18" WOA bbl.
(77gr. SMK) </div></div>

How many grains did u use to get that velocity??
 
#40
Re: cloning MK262 ammo

Once upon a time we could buy military brass with crimped in primers and this stopped the blown primer pockets.

These days one can pull the shitty green-tip bullets, re-size the neck, and reload some nice warm, but safe 262.

I got 2750 with N140 and N540, but I ain't gonna say what it was because I was using crimped primer brass from green tip pulls and I don't want to see a blown up rifle from my data.

Just a thought to you guys with some junk green tip.
 
#41
Re: cloning MK262 ammo

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: archad</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: longrange30</div><div class="ubbcode-body">I got 2803fps w/ TAC out of my 18" WOA bbl.
(77gr. SMK) </div></div>

How many grains did u use to get that velocity?? </div></div>


24.4gr. TAC/ Win. Brass/ 2.260"/ Fed. 205M Primer/ 77gr. SMK- its a little above MAX with Sierra's data but I showed NO pressure signs. I think Sierra's max is 24.0gr. w/ TAC.

I worked up to this load.
 
#43
Re: cloning MK262 ammo

I've been working on this recently as well. The most promising powders to date have been Varget, N140, AA2230, and TAC.

Highest velocities observed so far has been with 25g or TAC pushing a 77g SMK-C which averaged 2813 with no pressure signs observed. Unfired LC09 brass, Fed 205M primers, 2.260 COL and no crimp. Accuracy stayed about 1.5 MOA with this load in powder charges from 23.5 to 25. I plan to try different primers to see if I can get reliable sub MOA performance, but maybe the rifle just doesn't like cheap TAC.

Using 25g of Varget this load averages a bit under 2750 and just a tick over MOA. Again, no signs of pressure.

Weather for that day these numbers were taken was 74 degrees with low humidity at maybe 20' above sea level.


Saleen
 
#44
Re: cloning MK262 ammo

I ran out of MK262 Mod 1, so I worked up a "clone" that shot real fine in my rifle. It's a 10 year old Bushy Varminter with a 1:9 twist barrel that should NOT shoot the 77's well but it does. Just like the United Nations, your results may vary.

Brass: New, prepped LC09
Primer: Fed. GM205M
Powder: 24.6 RE15
Bullet: 77 SMK
Trim Length: 1.755
OL: 2.257-2.260
Base to Ogive: 1.859
Crimp: Just touch it (.001)
Barrel Legnth: 24"
Avg FPS: 2763
ES: 22
Temp: 12F
Humidity: 85%
BP: 30.26

This load continues to shoot well out to 750 yards. When you consider the rise in MV with temp increase, I'm sure it's doing 2800+ with no pressure. Quick Load shows this load as being very close to being compressed, but not near pressure limits. Work up slowly and be safe.
 
#45
Re: cloning MK262 ammo

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tnichols</div><div class="ubbcode-body">I ran out of MK262 Mod 1, so I worked up a "clone" that shot real fine in my rifle. It's a 10 year old Bushy Varminter with a 1:9 twist barrel that should NOT shoot the 77's well but it does. Just like the United Nations, your results may vary.

Brass: New, prepped LC09
Primer: Fed. GM205M
Powder: 24.6 RE15
Bullet: 77 SMK
Trim Length: 1.755
OL: 2.257-2.260
Base to Ogive: 1.859
Crimp: Just touch it (.001)
Barrel Legnth: 24"
Avg FPS: 2763
ES: 22
Temp: 12F
Humidity: 85%
BP: 30.26

This load continues to shoot well out to 750 yards. When you consider the rise in MV with temp increase, I'm sure it's doing 2800+ with no pressure. Quick Load shows this load as being very close to being compressed, but not near pressure limits. Work up slowly and be safe. </div></div>

That's pretty much the load I use to "clone" the MK262, the only thing I would add is that it's a really good Idea to trickel Re-15,as it does not "dump" well, being a stick power.

I tried TAC, but to get the velocity I was looking for, I had to run them pretty hot, (I pulled several lots of BHA MK262 mod1 rounds, and adveraged the powder charges, backed off 1/2 gr.) Still, my WCC and LC cases tended to streach about .025" after two loading, and the primer pockets were done. Gave up on that one quick, and ended up pulling about 200 loaded rounds. Be carefull, like the man said, this is the ragged edge of sanity in the 5.56mm. Better to be safe than stupid.
 
#47
Re: cloning MK262 ammo

sorry to necro post but whats the consensus on Varget? Im finding 25gr of Varget under a Nosler 77gr in Lake City brass with fed 100 seems a little hot.

24gr maybe?

Thats out of both a 16in BCM SS410 middy barrel with 1/8 twist and a 11.5in BCM BFH 1/7 barrel.
 
#48
Re: cloning MK262 ammo

I noticed just the other day that Ramshot is providing NATO velocity/pressure data for various popular boolits. Like say the 77SMK and the 70gr Barnes TSX.

TAC=much easier to deal with if you have a progressive press.
 
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