Gunsmithing AR gas hole size/leakage

[mercracing]

Two part question here. On an AR Is there a standard size hole that's drilled in the barrel for the gas system? I am working on diagnosing some problems with my AR and didn't know if there was a standard size hole. I'm running a 7" barrel.

Also. When I was taking apart the upper I noticed some leakage around both ends of the gas tube. I've heard leakage around the tube in the gas block is ok if the gun is running fine. Well, mines not running fine so I'm ordering an adjustable gas block from SLR and a new tube. My question was how tight is the gas tube supposed to fit in the bolt? Should there be much blow back along the gas tube?

Thanks for your input and HAPPY EASTER!!


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[nso123]

What is it doing when you say it is not running fine? There can be all sorts of issues from buffer springs to gas leaks. Short barreled ARs can be finicky sometimes.

 

[mercracing]

Long story short, I am getting FTE randomly. I have tried three different kinds of ammo. I am running an H3 buffer and a Wolff extra power buffer spring. I tried shooting with the normal spring and normal buffer and all combos of the four with the same result. I am ordering the gas block and a Bravo Company extractor upgrade as we speak.

 

[Turd in the Pool]

You're not helping things by not describing the function problem and throwing in the extractor upgrade. Is it short cycling, extractor failure?

 

[mercracing]

I dont think it is short stroking. I loaded one round into a mag and shot it. When I used Pmags, the bolt locked back and the brass ejected. When I used GI mags, twice the brass did not eject. The bolt pulled the brass out of the chamber and locked all the way back, but it did not eject the brass, it just sat on top of the mag.

 

[Gunfighter14e2]

4 different sizes are out there base upon barrel length, Google is your friend. Colt has 3 stds they use for the 20, 16 and the old xm177 series. Your over gassed,... and with a 7" barrel you need a pigtail gas tube....ymmv

 

[Dustbuster]

AR gas hole size/leakage

I went through that FTE crap when I built my first ar pistol. Now everyone I build gets a Wolff extractor spring and a small D ring under it. No more issues feeds and ejects like a dolphin at sea world 5 bucks per weapon to do this. My short stuff runs like sewing machines after I set the gas up. Make sure your gas tube lines up w no binding in the upper. Tune the gas system for the ammo you'll be running.
If for some reason u decide to run 22 lr through it you will get excess carbon build up that can clog the gas ports.i use a 1/16 drill bit to chase crud out of the barrel hole. I also take my time and make sure the holes in the block and barrel line up properly for max flow
Hope this helps


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[mercracing]

I ordered the bravo company upgrade for the extractor last night as well as an adjustable gas block. Hope one or both of these is enough. It's fun to shoot when it works!!


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[Dustbuster]

Cool I run 556 and 300 BO pistols they are fun to run!


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[Gunfighter14e2]

Building a weapon that will only run with certain brands or loading of ammo, is asking for issues down the road. YMMV

 

[mercracing]

Building a weapon that will only run with certain brands or loading of ammo, is asking for issues down the road. YMMV

I hear ya man. The goal for this project was to have a fun and cheap gun to shoot. Being able to go to any store and buy any ammo is the goal.


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