“Upgrading” gas block with dimpled barrel

Pbj ak

Pbj ak

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I have a barrel I’ve been using with a geissele gas block but wanted to switch to an adjustable gas block. I removed the old gas block and when I slide the new one in place the dimples for the set screws don’t line up. The barrel has been drilled through on the bottom to pin the gas block.

Can anyone give me some advice on what I should do? Keep the old gas block, get a new barrel, torque the set screws down and send it?

If I got someone at a machine shop to line up the “bottom pin hole” on the barrel with a drill press (or similar), clamp the barrel in place, then slide the new gas block in place, then drill a hole through the gas block and existing hole, would I still need to use the set screws?

May be a dumb question or I’m over thinking things. Any advise is appreciate.
 
This kind of thing can be done super ugly and still work. Some kind of flat or dimple is a good idea though. You can use the holes as a guide and just do it with a hand drill if you want to.
 
Pbj ak said:
I have a barrel I’ve been using with a geissele gas block but wanted to switch to an adjustable gas block. I removed the old gas block and when I slide the new one in place the dimples for the set screws don’t line up. The barrel has been drilled through on the bottom to pin the gas block.

Can anyone give me some advice on what I should do? Keep the old gas block, get a new barrel, torque the set screws down and send it?

If I got someone at a machine shop to line up the “bottom pin hole” on the barrel with a drill press (or similar), clamp the barrel in place, then slide the new gas block in place, then drill a hole through the gas block and existing hole, would I still need to use the set screws?

May be a dumb question or I’m over thinking things. Any advise is appreciate.
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Get one of these:


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KAK MULTI POSITION DIMPLE DRILL JIG - .750 SIZE

KAK MULTI POSITION DIMPLE DRILL JIG 4140 THRU HARDENED STEEL MAG PHOSPHATE FINISH FOR USE WITH .750 DIAMETER BARRELS DIMPLES BARRELS FOR GAS BLOCK SET SCREW SPACING OF .500 .470 .450 .425 .400 INCLUDES DRILL JIG 3/16 HSS 90 DEGREE SPOT DRILL POINTED SET SCREW FOR ALIGNMENT ALLEN WRENCH
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Keep the geissele gas block and change your buffer weights to properly gas your ar.

You can hack it up and the gun still run but I wouldn't be able to sleep at night. And adjustable gas blocks have wide varying degrees of success and extreme failure.

I had a hell of a time finding a gas block already drilled for cross pin that would fit a pencil barrel. Gunsmith told me he could cross drill a gas block although I didn't have him do it because I found a solution. I would dimple and cross pin if this is your last gas block and it is possible.
 
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Doesnt a company make an adjustable gas tube? I wish I could remember the name... but then it wouldnt matter what gas block you used.
 
Desolo said:
Doesnt a company make an adjustable gas tube? I wish I could remember the name... but then it wouldnt matter what gas block you used.
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Bootleg has an adjustable bcg also. Or change buffer weights
 
I'd use a clamp on gas block, or use the one you have and just re-dimple it. Nothing wrong with quality adjustable gas blocks.

Gun runs way smoother with proper gas flow. Buffer weights just increase the weight of the whole recoil system cycling.
 
NKD said:
Buffer weights just increase the weight of the whole recoil system cycling.
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It'll slow down your bolts speed. Most of your felt recoil in an AR is when the buffer slaps the buffer tube in the end of it's travel. Slow down the bolt with more mass in the carrier or by changing buffer weights and you'll have less recoil.

Edit to say if you're suppressed or have an abnormally large gas port then I understand the adjustable. I'm just more of a fan of getting it right and leaving it alone without adjustable means.
 
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Squanchy said:
It'll slow down your bolts speed. Most of your felt recoil in an AR is when the buffer slaps the buffer tube in the end of it's travel. Slow down the bolt with more mass in the carrier or by changing buffer weights and you'll have less recoil.

Edit to say if you're suppressed or have an abnormally large gas port then I understand the adjustable. I'm just more of a fan of getting it right and leaving it alone without adjustable means.
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Lots of barrel makers get carried away with port size beacuse of under powered ammo
 
Squanchy said:
It'll slow down your bolts speed. Most of your felt recoil in an AR is when the buffer slaps the buffer tube in the end of it's travel. Slow down the bolt with more mass in the carrier or by changing buffer weights and you'll have less recoil.

Edit to say if you're suppressed or have an abnormally large gas port then I understand the adjustable. I'm just more of a fan of getting it right and leaving it alone without adjustable means.
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I believe that when you add mass, you increase the feel of the bcg stopping and increase the forward motion from it shutting again. Adding weight certainly smooths out the feel. But imo, it increases the movement of the gun. With a low mass system, you decrease the weight and the gas. Gun just shoots flatter.

This is just my opinion. I agree with the idea of getting it right and leaving it alone. I just think that getting it right at the gas port is the ideal solution, but not the only solution. I agree if your gun is slightly overgassed, a heavier buffer will really improve it and it will definitely feel better.
 
NKD said:
I just think that getting it right at the gas port is the ideal solution
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This is absolutely the best answer.

There's just too many degenerates like me that do not clean their guns well and those little adjusting screws get locked up. Moral, don't be a degenerate, and if you are a knuckle dragger don't touch em lol
 
thanks for the replies fellas.

I guess I should have mentioned the reason I want the adjustable gas block is to cut down the gas in my face while shooting suppressed. I bought an aero precision adjustable gas block a couple weeks ago so I’d like to make it work if possible. I could use it on another upper I suppose but would still like to get an adjustable gas block on this upper.
Here are a couple pictures of the gas block and how the dimples line up. The first hole lined up (obviously) but the other has 50% off the dimple covered up. Also, in order to line up the first hole, the gas block isn’t seated against the shoulder. I’ve seen some uppers with a small gap and some without. Can anyone confirm if I should have a gap between the gas block and shoulder?

C9F7B82D-9C67-49E9-A037-A628B9573AB2.jpegCD11EE5A-89B2-4DA7-BC1B-53D8DE49F5AA.jpeg1407D029-B0BF-4664-8738-B02AE5DFA580.jpegC5959FD1-2541-4322-B81D-8CA833CD7D95.jpeg Here’s a picture of the original geissele gas block
990B61A4-71FC-4246-AE5E-029B61BC6772.jpeg
 
Desolo said:
Doesnt a company make an adjustable gas tube? I wish I could remember the name... but then it wouldnt matter what gas block you used.
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Black River Tactical

They have filled many of my needs/wants on builds.

blackrivertactical.com

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Pbj ak said:
Here are a couple pictures of the gas block and how the dimples line up. The first hole lined up (obviously) but the other has 50% off the dimple covered up. Also, in order to line up the first hole, the gas block isn’t seated against the shoulder. I’ve seen some uppers with a small gap and some without. Can anyone confirm if I should have a gap between the gas block and shoulder?
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I’ve never seen one properly aligned that acrually made contact with the shoulder. Usually a credit card thickness gap.

Depending on your charging handle, a little RTV and/or a small hole (if you’re a righty shooting a standard upper, or a lefty with a left-side ejection) will help.
 
You can adjust gas several ways:

- adjustable gas block
- adjustable gas key
- adjustable gas tube
- adjustable carrier

Maybe more?
 
BigWaylon said:
You can adjust gas several ways:

- adjustable gas block
- adjustable gas key
- adjustable gas tube
- adjustable carrier

Maybe more?
Click to expand...
Any thoughts on if I should try to redrill the second dimple that doesn’t line up just right? Or just stick with the original gas block?
 
Pbj ak said:
Any thoughts on if I should try to redrill the second dimple that doesn’t line up just right? Or just stick with the original gas block?
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Having never actually done it, I’d still probably recommend buying the jig and drilling the second dimple.
 
Ive only ever put one dimple in barrels. Most high quality barrels that come pre dimpled only have one opposite the gas port too. This is due to the exact problem you are dealing with. Too many different manufacturers of gas blocks with different spacing. A single dimple is more than adequate on a properly installed block. nevermind the fact the entire block is protected by the handguard. unlikely to have it shift if nothing can hit it.

the gap between the shoulder of the gas block journal and the gas block goes all the way back to the early days of the platform. drop in handguards needed the handguard cap that sits between the FSP and the shoulder. from a technical perspective, there should always be this gap regardless of what you are using because it ensures that the gas port on the barrel is centered inside the gas tube port.

based on the photo you posted, it appears to be a very short barrel. gas systems on short barrels can be finnicky until you add a suppressor. youll definitely want adjustable gas if you are going to be deidcated suppressed. the Black River Tactical gas tubes work well too. I have used several of them to tame down severly overgassed barrels that got permanently suppressed. however, if you plan to frequently swap back and forth between suppressed and unsuppressed a spec'd gas tube is going to be harder to get to that sweet spot and may require testing with multiple tube sizes until you find one that works with your system in its entirety. type of can, ammo, weight of reciprocating mass etc all factor into this.

an adjustable block is the right call, imo. it should be noted though that some of the adjustable blocks on the market dont do as well as others when you talk about continual adjustment. some of the blocks that have detents and springs can seize up and break. i prefer blocks that only use a single adjustment screw and a single set screw. set it and forget it.

the added benefit of using the adjustable gas block with your supressor is that you can get the reciprocating mass back down to a reasonable level and really make the gun shoot soft. no need for heavy springs and heavy buffers if you get the gas back down to a reasonable operating window. some of the softest shooters i have are dedicated supressed 5.56 with adjustable gas and lightweight components.
 
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Personally, I think that is an easy fix. Drill press would be ideal. Re-dimple it using block as the jig and be careful not to screw up the threads. Or better, clamp barrel in minivice and set bit, then remove block and drill. Been done a million times.

I have had blocks/barrels that go right to the barrel journal, so I always carefully measure with the proper device.
 
Milspec entails the front sight base being pinned -- which usually translates to a pinned gas block when they're part of said same. So, with that in mind, using the single dimple that lines up and then pinning the gas block with a roll or taper pin (your choice, but most seem to prefer roll pins) in the same way front sight bases are pinned would also be a way to go.

My take:
On my AR's intended for more than just plinking, I have all my gas blocks pinned. As there are different barrel shoulders, gas block shapes, sizes, etc, I have a smith do this for me because the jigs to accommodate all the variations are actually more costly than using a smith -- since I just don't have loads of AR's that require GB pinning
 
Pbj ak said:
Any thoughts on if I should try to redrill the second dimple that doesn’t line up just right? Or just stick with the original gas block?
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Re drill it .. I bought a tool for it.....first tool was out of spec they sent me another one that worked great
 
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