So im building a new upper which will be going on my sbr lower.. it will be a 12” 5.56 and have a saker 5.56k on it about 99% of the time. This will be my training upper and possibly pull some competition/duty roles.. i know the best route is to run an adjustable gas block since i will be better able to control the gas with it and its suppressed. But i know a lot of people advise against adjustable gas blocks for utmost reliability. What is you guys take? Go with fixed gas block and just tune with buffers and springs or go adjustable and not worry about it? I have a superlative arms adjustable on a different rifle that i have really liked but i only have several hundred rounds through it so not much to test its durability. Thanks
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New upper build... adjustable gas block or fixed?
- Thread starter black5.3
- Start date
For me, if it’s one of my training/carbine course/home defense ARs I much prefer to use a barrel with a proper gas port size and a pinned gas block. I use a 10.3” Daniel defense or Colt barrel with a 0.070” gas port, H or H2 buffer and full pressure ammo.
My plinking or “competition” ARs I use a SLR gas block. I choose the weakest ammo I think I’ll shoot with it and tune to that. I’ll use a standard or lightweight carrier with a standard carbine buffer and spring. Close the block and start to open the settings until it locks back on an empty mag. Then I give it one more click open from there. No issues at all with this method and running various ammo through them.
My plinking or “competition” ARs I use a SLR gas block. I choose the weakest ammo I think I’ll shoot with it and tune to that. I’ll use a standard or lightweight carrier with a standard carbine buffer and spring. Close the block and start to open the settings until it locks back on an empty mag. Then I give it one more click open from there. No issues at all with this method and running various ammo through them.
I run adjustable on anything out of the ordinary I use Geissele ss. Especially any I would a can on. My go to home defense guns no pinned A2. Easier to have it and not need then trying to keep chasing down fixes. Put a can on it see how it acts. Just my opinion
Yet another option might be something like a Bootleg Inc 4-position adjustable carrier. Easier than messing around with gas block adjustments, and full auto rated.
Bootleg Inc is a sister company to PWS, so it's GTG.
https://bootleginc.com/product/full-auto-adjustable-carrier/
Bootleg Inc is a sister company to PWS, so it's GTG.
https://bootleginc.com/product/full-auto-adjustable-carrier/
For an SBR length I would probably go with an adjustable block, but mostly plan to set it and forget it since you're dedicating it to work with a certain can. I don't know about the SLR block specifically, but some other designs will lock up after a while.
For an almost exclusively suppressed carbine configuration I don't think it's really warranted to have an adjustable block unless your gas port size is off. By the time the gas port starts eroding, the adjustment function will probably be locked up from use as well anyways. Suppressed I haven't seen a difference in cleanliness at all, maybe there would be a relative difference in an SBR length but I doubt it.
For an almost exclusively suppressed carbine configuration I don't think it's really warranted to have an adjustable block unless your gas port size is off. By the time the gas port starts eroding, the adjustment function will probably be locked up from use as well anyways. Suppressed I haven't seen a difference in cleanliness at all, maybe there would be a relative difference in an SBR length but I doubt it.
Adjustable gas block makes sense with your build and provides additional options down the road. You may want to change your setup which adjustable can accommodate.
Thanks for the info everyone, just wanted to mainly get other opinions on the setup and most everyone is for the idea of an adjustable gas block. I was leaning that way already anyway. I will probably stick with what i know and get the superlative clamp on gas block. The JP is cheaper but there is not as much about it online as there is for the superlative or slr.
Have jp and superlative. I prefer the superlative and have yet to have any type of failure. Although I’m not running suppressed and generally give a couple blasts of brake cleaner down the gas tube after a day of shooting.
I also vote adjustable gas block. It's nice to tune your gas to your particular setup. Plus.... from a reliability standpoint it's not like they default to a "fail closed" right? I'm not a high round count guy so my opinion probably doens't matter much, but I see an AGB failure as seizing up and not being able to adjust anymore. But that really doesn't have any impact on the function of the gun, you can still shoot it withing the parameters you set it up for.
I have a 300BLK SBR that's suppressed 100% of the time. I guess the gas port has to be sized big enough to run subsonic unsuppressed so it'll cover all the options for all the people. But with supersonic suppressed it really thumps. No big deal but an SLR really made it a lot nicer.
I have a 300BLK SBR that's suppressed 100% of the time. I guess the gas port has to be sized big enough to run subsonic unsuppressed so it'll cover all the options for all the people. But with supersonic suppressed it really thumps. No big deal but an SLR really made it a lot nicer.
My first experience with a adjustable gas block was years ago with an inch pattern FN-FLR (L1A1). Eleven detent positions, one no gas for blanks and grenade launching (or so I was told about the grenade launching). Anyway, rather than flinging brass into the next county and pounding the hell out of the bolt and receiver, it could be adjusted down to just eject brass into a convenient pile or into my toolbox on the bench. Next experience was with a Daewoo 100 with an adjustable block. Why a Daewoo? Just like the FN a side non reciprocating charging handle.
So with a large frame AR, an adjustable gas block seemed like the thing to do, JP in this case. The amount of shock/vibration when closed down to just reliably eject is noticeably less than wide open or the original fixed gas block. I figure it will have maybe a little less wear and tear over time. It helps with recovery time shot to shot too, a little less upset. Done properly a no brainer. Oh yeah, I prefer the clamp on variety vice the set screw or pinned and Loctite is you friend.
So with a large frame AR, an adjustable gas block seemed like the thing to do, JP in this case. The amount of shock/vibration when closed down to just reliably eject is noticeably less than wide open or the original fixed gas block. I figure it will have maybe a little less wear and tear over time. It helps with recovery time shot to shot too, a little less upset. Done properly a no brainer. Oh yeah, I prefer the clamp on variety vice the set screw or pinned and Loctite is you friend.
