Buffer Weight in MK 12 with A5 Extension

[Alaska3006]

I built a MK 12 with the 18" barrel and rifle length gas system.

I used the Vltor A5 Extension

what buffer weight do I use with the riffle buffer spring.

[dramabeats]

You will need to get an A5 buffer, start with the regular A5H2 and go from there.

[Iraqgunz]

My guess is that the gas port is the correct size. That being the case, it will work with the entire range of buffers. My FN MILSPEC 20" upper receiver uses the A5 with green Sprinco spring and 6.83 oz. buffer.

[Robb Jensen]

I use the 5oz A5 buffer in my BCM 18" rifle gas gun with a standard A2 buffer spring and I also shooting this with a Surefire Mini suppressor.

[Onyx Z]

Standard A5H2 here. Works flawlessly.

[Clint]

I'd start with the standard A5H2 buffer and spring that comes in the VLTOR kit.


I built a MK 12 with the 18" barrel and rifle length gas system.

I used the Vltor A5 Extension

what buffer weight do I use with the riffle buffer spring.

[Steel head]

With a .104 gas port mine liked the A5H3.

[BufordTJustice]

My Rainier Arms Mountain Series 18" with rifle gas ran on a Springco GREEN with the A5H4 on even the weakest ammo. Right now, i use the A5H2 with an adjustable gas block.

[Renegade04]

I use the LMT SOPMOD buttstock assembly on my Mk12 with a H2 buffer. It works really well.

[Iraqgunz]

I think that last time I measured one of those ports, it came in around .100. A 20" MILSPEC gas is .093


My Rainier Arms Mountain Series 18" with rifle gas ran on a Springco GREEN with the A5H4 on even the weakest ammo. Right now, i use the A5H2 with an adjustable gas block.

[Steel head]

I think that last time I measured one of those ports, it came in around .100. A 20" MILSPEC gas is .093

Mine is a rainier UM, check it with pin gauges before I built it.
I'm wondering if the mountain series it the same size.

[BufordTJustice]

I think that last time I measured one of those ports, it came in around .100. A 20" MILSPEC gas is .093
Rainer stated it should be right around .098 to .100 for the 18" mountain, so it sounds like they are about where they need to be according to your measurements.

I used a buddy's cheap pin set and mine seems to be between .098 & .099.

[Clint]

I believe the proper size for a Mk 12 (18" rifle) gas port is .0995" (#39 drill),
So it looks like Rainier nailed it.

[Slvr Surfr]

I have the standard 5.3 oz A5 system on my 18" BCM rifle length system. Runs like a top with all the ammo I have put through it.

[Iraqgunz]

Yep, that's correct. And most prints I have seen state +/- .001 on there.


I believe the proper size for a Mk 12 (18" rifle) gas port is .0995" (#39 drill),
So it looks like Rainier nailed it.

[Alaska3006]

Thanks I will start with the standard 5.3 Oz A5 buffer........

[Clint]

Sounds good.

BTW, the last A5 buffer I received actually weighed 5.40 oz.




Thanks I will start with the standard 5.3 Oz A5 buffer........

[Alaska3006]

I have been using a Carbine extension with a Colt H Buffer 3.8 OZ and a CS Enhanced Carbine spring from Damaged Ind.

I just recently switched to the Vltor A5 system with a Tubbs Flat Wire buffer spring..........super sweet

[Alaska3006]

My mK 12 has the crane .102" gas port douglas done by Frank White........