Adjustable Gas Block and Buffer System for First 308 AR Build

[MaineMan2]

I'm an older M1A guy moving to the dark side.  Have built more than one AR-15.

18.5" barrel with rifle length gas system and .936" gas block journal.  From everything I've read and heard, 308 ARs really benefit from an adjustable gas block even if I never intend to suppress this rifle.  Adjustable gas blocks range in price from $60 to over $200.  JP Enterprises and SLR both appear to make quality adjustable gas blocks, but I am open to any suggestions.

Until this morning, I thought I'd be GTG with a 308 Carbine length buffer tube, buffer and spring.  The CAR-10 system from HeavyBuffers seems to get good reviews.  However, I just talked with 2 manufacturer techs and they both steered me toward a rifle length buffer tube and fixed stock.  This isn't a close-quarters build by any stretch of the imagination so a fixed length of pull would be fine.  Also, it would be nice to leave the door open for a second upper with a 22" 6.5 Creedmoor barrel for serious accuracy at longer ranges.  So is a carbine length buffer system more problematic than a rifle length system?  One thing I don't especially like about a fixed stock is more weight.

I appreciate your help on this!

Chip

[shooterrex]

Hi. Most "problems"with the carbine stocks is vendors try and sell AR-15 parts to handle a lot more mass.

If you want a carbine set up this one works.

https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories&Category=4eeff98b-d9a6-40fd-be6b-ab2e44ec1080

If you have the right size gas port in the barrel you don't need an adjustable gas block if you are not going to suppress your rifle.

[jtallen83]

^ Yep, that carbine recoil system WILL run. With that recoil system and and the proper sized gas port you shouldn't need an adjustable block. I have an AR-10 I run suppressed without one, just used one of Heavy Buffers spring and buffer sets.

[98Z5V]

9 hours ago, MaineMan2 said:

  So is a carbine length buffer system more problematic than a rifle length system?  One thing I don't especially like about a fixed stock is more weight.

I appreciate your help on this!

Chip

Chip, this will answer just about any question you have on recoil systems, and most other gas system questions.  If you need to ask anything about this article, just hop back in here in this thread, and ask away.  

 

[MaineMan2]

44 minutes ago, 98Z5V said:

Chip, this will answer just about any question you have on recoil systems, and most other gas system questions.  If you need to ask anything about this article, just hop back in here in this thread, and ask away.  

Thank you very much!  TL:DR I'm going with a rifle length receiver extension, a true 308 AR buffer (5.3" long and 5.6 oz) and spring, and a fixed stock.

That thread cut through a lot of the mess I've been trying to sort out.  At least I listened when a tech from Fulton Armory and another from Aero Precision both advised me to stick with a rifle length buffer system.   That first pic alone is extremely useful information. You also posted a great pic of an AR-15 vs. AR-10 gas tubes.  I'm not especially a fan of GarrandThumb, but he gave me an "ah ha!" moment when he explained what happens when you compensate for a really short dwell time by making the gas port a lot bigger.  It explains the "why" behind so many manufacturers trying to compensate for this change with that change, on and on ad nauseam.  Also the quest for a "universal solution" to a dog's breakfast of potential parts combinations.