Adjustable Gas Block and Slim Handguards

[Nowind0]

I am starting to purchase parts for an upper build and plan on running a low mass BCG and a mid-length gas system. I have a couple of questions as I have never run an Low Mass BCG previously.

1. Is it required to run an adjustable gas block or is it just a nice to have.

2. I would like to run a slim handguard. (15" Vltor Freedom Rail) with a ID or 1.38".  What Adjustable Gas Blocks would fit inside a rail of that dimension?

Thanks in advance.

[Stuey]

Adjustable gas block is not required unless you are running a suppressor. Some people like to have them for regular loads. I only have it for my suppressor and when I take it off click I back to normal.


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[SlvrDragon50]

SLR posts dimensions of their gas blocks. I use a SLR Helix + gas block since I knew that combo would work together (also they're local). I think Superlative does as well, but you can send them a message asking for dimensions.

 

The only other adjustable gas block that seems to do well is the Wojtek.

http://www.wojtekweaponry.com/wojtek-weaponry-625-adjustable-clamp-compression-gas-block/

[Steve133]

I wouldn't go as far as to say that an adjustable gas block is required if you're running a low-mass BCG, but I don't think you're really going to reap much benefit from the low-mass BCG without being able to tune the gas settings on the rifle. In fact, it might be counterproductive - I'd think that the addition of a low-mass BCG would only make the overgassing that most fixed gas blocks cause even worse.

 

Are you dead-set on that specific handguard because you already have it on-hand, or are you just planning on buying it because you like it for whatever reason? If the former, then like SlvrDragon said, most manufacturers post mechanical drawings of their gas blocks for exactly this reason, so you're probably just going to have to check them all one-by-one until you find one that will work. If the latter, then I'd recommend taking your gas block selection into account when selecting a handguard - I've found it easier to consider those components as a system and select them at the same time, instead of picking one and then finding a model of the other that will work with I've already picked.

 

All of that said... most "low-profile" adjustable gas blocks will fit under most handguards, but you definitely want to do your homework to confirm that before you buy anything.

 

[TonytheTiger]

Standard procedure for me is to buy whatever I want and expect to shave high points off the gas block and ream out the handguard. Even when they fit I'm usually not thrilled with the amount of clearance.

 

Steve133 is right, lowering your reciprocating mass without also lowering the amount of gas running it will make you more overgassed and can make the gun very snappy.

Edited August 27, 2018 by TonytheTiger

[PacMan]

Answers:

 

1) Yes.  No reason to go to low mass BCG without tuning the gas flow.  Does not mean adjustable gas block is the only way, see below ***

 

2) The slimmest and most reliable adj. gas block out there is SLR Sentry.  It should fit the 1.38" since mine is a Solo which has a published ID of 1.3" and I'm using the Sentry 7 set screw block.

 

*** The other solution to obtain gas flow regulating is an adjustable bolt carrier group.  2A Armament Lightweight BCG in either steel or titanium.  Not cheap but racing parts aren't.  The Titanium BCG weights in at 5.9 oz complete, in the realm of aluminum bolt carrier group without the drama.

[RAINY0DAYS]

I'm using a handguard with a 1.30 ID with an SLR sentry. Had to take some material off the inside of the handguard, but it's not a big deal.

I think the absolute slimmest gas block design I've seen is from master of arms.

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[Frankly]

Rubber City and Taccom make or made adjustable gas KEYS that work fine too.

[troupe]

SLR here also. I used both SLR gas block and hand guard.  When I back off 3 gun in competition, I used a normal gas block and the Matrix hand guards. Very inexpensive, but not the same as a tuned gas system and LMBC group for competition.

[PeterrSmall]

The gas block is adjustable, so you don't have to constantly readjust it. You set the wrench on the bolt and tighten it, and it stays where you've set it. These blocks are designed and built to last. Because gas blocks are metal and not plastic, they also heat up less. They stay more relaxed, and they don't meltdown. When you tighten the bolt, the bolt heats up and expands. My advice is to get one from https://elementarmament.com/product/odin-works-adjustable-gas-block/. They will last longer and also are made from high-quality materials.

Edited October 5, 2021 by PeterrSmall

[Bad_Karma]

I run the Odin Works adjustable gas blocks as well. Never had an issue and cheaper than Superlative Arms and SLR. 

[Stuey]

12 minutes ago, Bad_Karma said:

I run the Odin Works adjustable gas blocks as well. Never had an issue and cheaper than Superlative Arms and SLR. 

I had a Odin Works adjustable gas block and a screw broke after 50 rounds.  I had to drill it out to get it fixed.  Was not happy, pay the extra and get an SLR.

[Boomstick303]

The adjustable gas block is one of the major components that create a soft shooting AR.  I would not install light weight BCG and Buffer system without one.  You would need the mass of a normal BCG and buffer if you were to use a normal gas block.  If using a normal gas block with light weight BCG and buffer the rifle may malfunction and/or prematurely wear out parts.  Light weight BCG tend to not be cheap. 

 

Make sure you do your home work to make sure the gas block fits under the rail.  Both will typically have the diameters in their specs.  I try to stick with Low Profile Adjustable Gas Blocks.  I would call whoever you go with in regards to a rail to verify the gas block you are interested in fits under the rail if you think its a tight fit.  Being diligent up front will save you tons of headaches, time, and money on the back end.  

[troupe]

When you get the right combo, it will shock you. You will think you switched to a 22LR.

[Boomstick303]

3 hours ago, troupe said:

You will think you switched to a 22LR.

 

I built up a rifle with reliable parts, normal gas block, full mass BCG and Buffer and shot it in a couple of matches this last weekend to see how she ran. Forgot how much of a difference all that stuff made when I went to shoot the long range course and did not have the rifle butted up against my shoulder correctly. That was a surprise lmao. I forgot what a normal AR recoil impulse felt like. 

[Stuey]

15 hours ago, troupe said:

When you get the right combo, it will shock you. You will think you switched to a 22LR.

This is very true.  When I got mine done correctly, I thought I messed up my gun till I saw the holes down range.

[PacMan]

I've played with quite a few adj. gas blocks and as the free float tube gets smaller and smaller, their inside diameters don't play nice with the gas blocks even the low profile ones, so I've switched over to trimming the gas at the carrier using either an adjustable gas key (Rubber City Armory) or adjustable carrier (2A).  With the adjustable gas key in a lightweight BCG, I have been able to 'modernize' the old M16A1 style AR to a much softer shooting rifle (granted, it doesn't have much recoil in the first place) for the last match outing.

 

[kurtm]

You can always cut a small clearance window around the gas block if it's too close.

As for must have adjustable block....nah! I run my Aluminum carrier fully gassed and it is a very flat rifle. I found that I seemed to be waiting on it if I turned it down, but to each their own.

[K-Tex]

I agree on what most gave posted before me?   I have adj gb, adj BCGs and adj keys.   The adj gb is and has been a better choice.  I have also run a lmass BCG with a lighter buffer, but used a stronger buffer spring as for it increased dwell time for softer shooting.   No adj gb was used.   SLR and Odin adjustable (not set screw type) GBs are the better 2 I've used.   Going mid over carbine is usually a better choice?