Mid Gas system on a Carbine

[Red Belly]

I have a carbine AR15 (5.56) with collapsable stock. I am running it with an H buffer and FA BCG.

I want to build a MK12 type precision upper,18" barrel etc to run on my carbine lower.

My question is what is the recommended set up for this? Right now I am leaning toward mid length gas system & FA BCG. I think a rifle length gas system may give me some issues.

Thanks for the help.

 

[LongArm]

Re: Mid Gas system on a Carbine

mid length will work the best without having to tinker with it.

 

[TP4]

Re: Mid Gas system on a Carbine

I run mid-length gas systems on my 16" and 18" builds.

 

[carbinero]

Re: Mid Gas system on a Carbine

why not go intermediate?

definitely do the FA carrier.

 

[Red Belly]

Re: Mid Gas system on a Carbine

I am looking at a WOA barrel. The 2 choices are either rifle or mid length gas system.

 

[Dtarget]

Re: Mid Gas system on a Carbine

I would go for the rifle length gas system. If you plan to use a fixed front sigh, the longer sight radius is a plus. 18" barrel with rifle gas is a fairly common set up. Doesn't the real Mk12 use an 18" barrel with rifle gas?

 

[Strangedays]

Re: Mid Gas system on a Carbine

I would go mid. Run a rail or free float tube then you can have a longer sight radius.

 

[Red Belly]

Re: Mid Gas system on a Carbine

Yes. The MK12 is a rifle gas system.

 

[-=boone=-]

Re: Mid Gas system on a Carbine

WOA 18" SPR MID

 

[Red Belly]

Re: Mid Gas system on a Carbine

How does she run sir?

 

[-=boone=-]

Re: Mid Gas system on a Carbine

It runs well. It would probably run better with an actual AR15 shooter behind it. It has been a constant learning curve for me. I've shot golf balls at 400 with it.

I'm still testing ammunition at this point. 5 shot groups.

75 Grain HSM Match has been the winner so far. Solid ¾ Moa groups with some ½ moa groups.

I still have to order the 77 Grain HSM to test.

77 Grain Black Hills re-manufactured match Is absolute shit out of my rifle. 1.5 -2 Moa or larger groups. That really blows when you purchase 200 rounds of it. If you don't reload test ammo in smaller quantities.

XM193 55 Grain shot gun patterns. 3 Moa or greater.

PMC 55 Grain, 1-1.5 moa groups. I can order 1000 rounds of this for $300.

 

[Red Belly]

Re: Mid Gas system on a Carbine

I will be hand loading for it. Thanks for the info.

 

[uscbigdawg]

Re: Mid Gas system on a Carbine

On an 18" barrel, go rifle length gas. Smoother gas impulse and in my opinion, inherently more reliable.

Rich

 

[carbinero]

Re: Mid Gas system on a Carbine

Since it's custom made, with the correct gas port diameter, you shouldn't have a problem. Issues sometimes occur when people cut down a 20" to an 18" without taking that into account. So given those choices, I'd also go rifle.

 

[splean]

Re: Mid Gas system on a Carbine

Unless you really want the look of a covered gas block I would suggest the rifle length gas system for the aforementioned reasons. Good luck.

 

[Michaelvoigt1]

Re: Mid Gas system on a Carbine

Having had both the mid and rifle length systems on 18" barrels, I would definitely go with a rifle length gas system on a new 18" build.

You will have lower gas pressure operating the bolt carrier, resulting in a smoother recoil impulse. You have plenty of barrel in front of the gas hole to provid\e a proper gas dwell time.

I have not seen any advantage running a shorter than necessary gas system. They are always found a shorter gas sytem sharper in recoil and more prone to tearing up brass due to quick opening (some times resulting in malfunctions from filling the ejector hole with shavings).

MV

 

[Red Belly]

Re: Mid Gas system on a Carbine

Thanks gents. I think I have decided on the rifle system. I just read an article from a good friend about gas port location etc. It pretty much summed up what you guys have been saying.

Thanks again & happy new year to all.

 

[JLR]

Re: Mid Gas system on a Carbine

Good choice you made. Rifle length gas systems are the way to go on 16-18" barrels....they just seems to shoot softer.