Adjustable gas blocks on target ARs

[citizenconn]

I do a lot of bench target shooting out to 1200 yards with different caliber AR-15 and AR-308 rifles. I built all of these rifles with a standard gas block, but I am thinking of installing an adjustable gas block on a few of them. And then cutting off the gas flow completely.

The reasons for this are as follows: 1) So I don't have to chase my brass, as my Dad reloads almost all of our ammo. I use a brass catcher on my rear charging AR-15s, but there isn't one I've found that works well on AR-308 size rifles or any side charging ARs. And none work well with my AR-308 rifles, as they often seem to cause misfeeds of some sort. I'm left-handed and even using a brass catching net on the shooting table is cumbersome to say the least. 2) To see if there is less felt recoil since, in theory, most all the gas would be pushed forward in this set-up. 3) Probably some unknown known I don't know yet.

I have a number of side charging ARs and I figure I would setup some of these first to see if an adjustable gas block would have these operate like a de facto bolt action rifle. Is there anyone using ARs set up like this? Is my thinking wrong or is there a better way I should be considering? I would just take off the gas blocks but I figured there might be issues with the gas still escaping the gas hole in the barrel, and I don't know if there is a way to effectively plug that up besides using an adjustable gas block.

citizenconn

 

[wesmonster]

If you’re talking permanent, I suppose you could either just pinch your gas tube closed or remove it and slide your fixed gas block a quarter inch forwards or back which would effectively block off your barrel gas port.

There’s also a BCG designed for suppression that has a bleed off adjustment in the carrier accessible from the ejection port, Blackjack maybe?

Pretty sure any gas tube plug like the ones designed for rimfire conversions would blow out under centerfire pressure.

I suppose you could also cut down your BCG gas key so it can’t seal but you’re still gonna get gases in the action.

 

[citizenconn]

If you’re talking permanent, I suppose you could either just pinch your gas tube closed or remove it and slide your fixed gas block a quarter inch forwards or back which would effectively block off your barrel gas port.

There’s also a BCG designed for suppression that has a bleed off adjustment in the carrier accessible from the ejection port, Blackjack maybe?

Pretty sure any gas tube plug like the ones designed for rimfire conversions would blow out under centerfire pressure.

I suppose you could also cut down your BCG gas key so it can’t seal but you’re still gonna get gases in the action.

Thanks. Those are some good recommendations, especially moving the gas block slightly.

 

[Laphroaig]

2) To see if there is less felt recoil since, in theory, most all the gas would be pushed forward in this set-up. 3)

I'm thinking shutting off the gas is going to slightly increase recoil. It's pretty standard thinking that gas guns recoil less. The extra gas moving forward is going to result in an equal but opposite reaction, backwards.

 

[citizenconn]

I'm thinking shutting off the gas is going to slightly increase recoil. It's pretty standard thinking that gas guns recoil less. The extra gas moving forward is going to result in an equal but opposite reaction, backwards.

Yes, thanks for that observation. I use side chamber muzzle brakes on all my target ARs, pretty substantial 3-4 chamber ones on my .308, .260, 6.5 CR, .450 BM ARs. But I am interested to see side by side on gassed/non-gassed guns just how much the recoil impulse will change.

 

[bfoosh006]

If you decide on an Adjustable Gas Block... be aware, they tend to get sticky with carbon build up. So proper maintenance is important.

Also... make sure any Adj GB has easy access to the adjustment screws, less expensive ones tend to have side adjustments... and the better ones have the adjustment screw towards the muzzle... and have positive tactile clicks.

I run mostly SLR's and some Aero Precision's ... those both are a linear adjustments. I have never tried turning either one completely off. That said I run the SLR's 6 clicks opened from closed ( 15 clicks available ) and all my various barrel lengths, and brand narrels , and all the 6.5CM's and 308's still function 100%.
The brass ejection "pattern" is considerably more manageable compared to the OEM setups ( excessively gassed on all barrels )

I wouldn't feel the need to completely close down the gas... the brass is not being flung anywhere near as far with the constricted gas flow.

I will also suggest trying this Adj GB... ( I am going to on the next build )
They aren't cheap... but the benefits of the design are worth to to me. You will need a "straight" gas tube from them

https://www.riflespeed.com/LEMIL-Gas-Controls-_p_34.html
https://www.riflespeed.com/LEMIL-Gas-Controls-_p_34.html
They have a fancy guide to help you select the "correct one"
https://www.riflespeed.com/Technical-Documents_p_19.html

 

[jak67429]

What I did on mine mostly because it was so overgased it was breaking extractors. I switched to a adjustable gas block and set it so the gun would just barly cycle. Now the brass drops about 1 foot to the right of me when shooting prone. Also try the brass goat, it snaps over the mag well of an ar. I have one for ar15 and have used it on ar9 ar15 running 223, 6.8spc, 6.5 Grendel and a 300 blk.

 

[greyling22]

yes, moving your gas block a little will cut off the gas. heck, you don't even need a gas tube if you cut the gas off. Keep in mind that manually cycling the gun will still kick your brass out. And it might be hard to extract. I don't know. The simple gas block that aren't click adjustable do rapidly seize up with carbon. Turning the gas WAY down will reduce recoil and keep your brass in this county. All AR's should run adjustable gas blocks. all ar's are over gassed by design for utmost reliability. I don't need that.

While there might be a little more recoil with a gun that isn't being gas operated, I think the lack of reciprocating mass bouncing around, and lack of ejection port blast would probably more than make up for it.