Cloning MK262 the quest (kinda)

[indydave]

So we start with 75 grain hornady BTHP first up is PMC brass, trimmed, with inside neck debur with a VLD reamer/ outside debur with rcbs tool. primer pockets reamed with a hornady reamer/
johnnys reloading on utube did a long series on this i will start with AA2520 seated with redding match dies with crimp die. starting at 25.0 grains and working up to western powders max data for 556 nato load data. We will then try cci 400 rem 71/2 and winchester primers. after that test H335 and WC844 and H4895
test mule is a 223 wylde 1 in 8 twist 18 inch barrel

see if we can make 2800 ish FPS with sub MOA

 

[jsn_mooney]

I got where you are trying to go with RL-15 in wolf gold primed cases. I went with those cases because the primers are staked.
You are on the right track- you'll never get there with .223 data.
Good luck, and be safe

 

[DadSmith]

So we start with 75 grain hornady BTHP first up is PMC brass, trimmed, with inside neck debur with a VLD reamer/ outside debur with rcbs tool. primer pockets reamed with a hornady reamer/
johnnys reloading on utube did a long series on this i will start with AA2520 seated with redding match dies with crimp die. starting at 25.0 grains and working up to western powders max data for 556 nato load data. We will then try cci 400 rem 71/2 and winchester primers. after that test H335 and WC844 and H4895
test mule is a 223 wylde 1 in 8 twist 18 inch barrel

see if we can make 2800 ish FPS with sub MOA

Varget and H4895 will get you close but not with 223 Remington pressures. You might get 2750fps.
5.56x45mm pressure you will get close or right at it. 26.5gr CFE 223 is maximum load. You should work your way up. CFE 223 seems to shoot most accurately at the higher end I've found in my rifles, but every rifle is different.

 

[avboiler11]

23.5-23.8gr 8208XBR under a 75-77gr HPBT match bullet. In my experience, brass and primer didn't really matter.

It'll lag BHA Mk262 by maybe 15-20fps, but be more accurate.

 

[DadSmith]

23.5-23.8gr 8208XBR under a 75-77gr HPBT match bullet. In my experience, brass and primer didn't really matter.

It'll lag BHA Mk262 by maybe 15-20fps, but be more accurate.

What length barrel? Is it 18"? That's a strong load for even 5.56.

 

[avboiler11]

What length barrel? Is it 18"? That's a strong load for even 5.56.

18" rifle gas & 16" mid 223 Wylde chambers, 12.5" & 10.5" carbine 5.56 chambers.

IIRC, 23.2gr XBR was/is max load for a 223 Rem Chamber with a 77gr SMK.

I've run as high as 24.0gr XBR under a 77gr Nosler CC which matched BHA Mk262 velocity but couldn't maintain 5 shots into 1.5" @ 100yd prone off a bipod from a SPR with 10x optic.

23.8gr was most accurate of every load tested, 5 shots into about 0.6" @ 100yd, but I ultimately settled at 23.5gr because it was faster than 23.2gr while giving a little extra pressure headroom for elevated temps, and easily put 5 shots into <1" @ 100yd.

I've run this load through RP, S&B, Wolf, LC and Lapua brass, loaded to 2.25" COAL, and never had any issues. I normally use CCI-450s with my Mk262 clones, but have run -400s and never seen cratering/flattening let alone experienced piercing.

AS ALWAYS...YMMV, caveat emptor, work up carefully.

 

[DadSmith]

18" rifle gas & 16" mid 223 Wylde chambers, 12.5" & 10.5" carbine 5.56 chambers.

IIRC, 23.2gr XBR was/is max load for a 223 Rem Chamber with a 77gr SMK.

I've run as high as 24.0gr XBR under a 77gr Nosler CC which matched BHA Mk262 velocity but couldn't maintain 5 shots into 1.5" @ 100yd prone off a bipod from a SPR with 10x optic.

23.8gr was most accurate of every load tested, 5 shots into about 0.6" @ 100yd, but I ultimately settled at 23.5gr because it was faster than 23.2gr while giving a little extra pressure headroom for elevated temps, and easily put 5 shots into <1" @ 100yd.

I've run this load through RP, S&B, Wolf, LC and Lapua brass, loaded to 2.25" COAL, and never had any issues. I normally use CCI-450s with my Mk262 clones, but have run -400s and never seen cratering/flattening let alone experienced piercing.

AS ALWAYS...YMMV, caveat emptor, work up carefully.

A guy ran 24gr in his awhile back and was blowing out his primers. Of course every rifle is different.
I know another guy that was running 24.2gr out of a 20" barrel with some flattening of the primer. Can't remember his combination though. IIRC 22.5gr was what my rifle liked with 75gr Hornady HPBT match bullets velocity was around 2500fps out of a 16" barrel. It avg around 0.75 moa out to 400yds. Which is about all you can squeeze out in this area with the trees and rolling hills and farm land.

 

[Creedmoor]

What length barrel? Is it 18"? That's a strong load for even 5.56.

I have run that with no problems in autoloaders, in bolts I pierce primers.

 

[Hohn]

A guy ran 24gr in his awhile back and was blowing out his primers. Of course every rifle is different.
I know another guy that was running 24.2gr out of a 20" barrel with some flattening of the primer. Can't remember his combination though. IIRC 22.5gr was what my rifle liked with 75gr Hornady HPBT match bullets velocity was around 2500fps out of a 16" barrel. It avg around 0.75 moa out to 400yds. Which is about all you can squeeze out in this area with the trees and rolling hills and farm land.

I run 23.6 of 8208 under an 80 ELD in my 5.56 chamber. Not mag length OBV but probably similar pressure as a mag length 77? Maybe less.

 

[Hohn]

So we start with 75 grain hornady BTHP first up is PMC brass, trimmed, with inside neck debur with a VLD reamer/ outside debur with rcbs tool. primer pockets reamed with a hornady reamer/
johnnys reloading on utube did a long series on this i will start with AA2520 seated with redding match dies with crimp die. starting at 25.0 grains and working up to western powders max data for 556 nato load data. We will then try cci 400 rem 71/2 and winchester primers. after that test H335 and WC844 and H4895
test mule is a 223 wylde 1 in 8 twist 18 inch barrel

see if we can make 2800 ish FPS with sub MOA

7.5s are super accurate primers but the cups might be a bit soft for pushing pressure to mk262 levels. 7.5 for me will crater much sooner than 450s or 41s. I don’t use 7.5s for hot AR loads.


If you want to clone mk262 and you’ve watched the JRB series, then you know very few powders can get you close to that performance without massive pressure. AA2520, PP2k, PP Varmint worked. AR Comp, H4895, Varget, N540, etc all hit pressure before they achieved the 262 velocities and the accuracy wasn’t always there.
My advice would be to drop down about 50fps and shoot for 2700 in an 18” tube. This makes a lot more powders viable.

My “defense” loads are either 75 Gold Dots or 75 Hornady BTHPs with cannelure. Both get the same charge of 2520 or pp2k. I haven’t accuracy tested them because honestly a defensive load doesn’t need to be that accurate. No such thing as self defense at 80y in most cases.

 

[Squid556]

I’ve been shooting the 262 clones for years. Recipe I enjoy is 23.8 Varget under the Hornady 75 bthp, then federal small rifle match primers.

 

[indydave]

25.1 grains of AA2520 in prepped pmc brass.

 

[Paul 7.62]

Try 24.2 grain of Power Pro Varmint with a 77 grain Sierra in a 223 Lapua case good in a 18" barrel for 2750 and 2880 in a 24" bolt gun