MK 262 Mod 1 5.56 Long Range

[gunner336]

Bought some Black Hills USGI MK 262 Mod 1 in GI box of 20's NOT the factory Seconds. Have now been told that I should NOT fire this in my Factory Rem 700 Bull BBl marked .223 Rem.
I was told the pressure is too high for a bolt gun. is this true???

 

[Dogtown]

Re: MK 262 Mod 1 5.56 Long Range

It's a hot load and outside of SAMMI .223 specs.

 

[Sig685]

Re: MK 262 Mod 1 5.56 Long Range

I doubt it's too hot for a bolt gun, especially a 700 and the 77gr SMK has a different ogive that does not put the bearing surface on the lands so there would not be the danger of extra pressure at ignition time caused by the bullet touching the lands.

My concern would be the twist rate of your rifle; if it's not fast enough the bullet will tumble. You need at least a 1:8 to have a chance, faster is better.

 

[Scotts556]

Re: MK 262 Mod 1 5.56 Long Range

Bad idea 5.56 has a longer lead than a sammi spec .223 remington. You could possibly get high pressure and KABOOM.


Scott

 

[Sig685]

Re: MK 262 Mod 1 5.56 Long Range

Scott is incorrect on many counts. I have never heard of "sammi spec" .223 Remington. The 5.56 chamber does indeed have a longer leade (not lead) but it doesn't matter with the 77SMK because as I pointed out earlier, the shape of the ogive is different.

Also, the 77SMK sticks pretty far into the case and while I am not aware of any SAAMI specifications for this bullet in .223, I doubt there is enough powder space to generate too much pressure. I replicate this load with LC cases and 24.5gr of Varget.

This cartridge is not the 5.56 NATO round your mother warned you about.

 

[Scotts556]

Re: MK 262 Mod 1 5.56 Long Range

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body">Scott is incorrect on many counts. I have never heard of "sammi spec" .223 Remington. The 5.56 chamber does indeed have a longer leade (not lead) but it doesn't matter with the 77SMK because as I pointed out earlier, the shape of the ogive is different.

Also, the 77SMK sticks pretty far into the case and while I am not aware of any SAAMI specifications for this bullet in .223, I doubt there is enough powder space to generate too much pressure. I replicate this load with LC cases and 24.5gr of Varget.

This cartridge is not the 5.56 NATO round your mother warned you about. </div></div>


I stand corrected. i have always been warned about 5.56 un a .223 marked gun so i avoid 5.56 in my 223 marked guns.

scott

 

[justpete]

Re: MK 262 Mod 1 5.56 Long Range

FWIW:

http://www.thegunzone.com/556v223.html

and embedded in the above:

http://www.fulton-armory.com/556-vs-223-Chambers.htm

 

[gunner336]

Re: MK 262 Mod 1 5.56 Long Range

Funny how there is so many opinions on a technical question but that is what makes this such a great forum.

so i am too assume that it is safe to shoot in my Rem 700. if not I guess I can sell then ammo. It is USGI not the black hills Seconds they sell.

 

[Sig685]

Re: MK 262 Mod 1 5.56 Long Range

What is the twist rate of your barrel?

 

[gunner336]

Re: MK 262 Mod 1 5.56 Long Range

Have no idea. It is a factory gun. The old standard Rem 700 but with the bull BBL. Factory stock gun with a timmey trigger but a good shooter.

 

[Sig685]

Re: MK 262 Mod 1 5.56 Long Range

My guess is that it's probably a 1:12 and it simply will not stabilize the 77gr SMk bullet. To be certain, I would simply use a cleaning rod and a marker and measure the twist rate, but since it's an older rifle, I can almost guarantee it's a 1:12.

So the answer is to not shoot it in this rifle, it's a waste of time and fine ammo.

You could use the ammo in an AR-15 with a 1:8 or 1:7 twist, if you have one.

 

[gunner336]

Re: MK 262 Mod 1 5.56 Long Range

Thanks for this info. I have a shorty M-4 but I thought this ammo was more for long range accuracy. Anyone looking for some MK 262???

 

[justpete]

Re: MK 262 Mod 1 5.56 Long Range

OK I gotta ask - where the heck do you get USGI Mk262 Mod 1 ammo? I must not get out much 'cuz I've never seen it. Cosmetic blems yeah, got a bunch, but issue ammo? Hmmm. Anybody?