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View Full Version : Using air pressure to check gas block on an AR


Falstaff
09-10-2010, 8:44 PM
In another thread, I posted how I was concerned that the gas block I installed on an upper was not lined up with the hole in the barrel. One of the suggestions was to use an air compressor to see if the air was passing through. I thought that was a great idea so I did so by plugging the breech with an foam ear plug and my finger, and inserting the rubber end of an air blow gun into the barrel (after removing flash hider). Anyway, it felt like alot of air was coming out of the gas tube so I'm 99% sure she'll function (havent tried it yet) but I was wondering if 150 psi air pressure would be enough to cycle the bolt back at all? (I didnt try it with the bolt carrier assembly, and I didnt think to use an empty shell casing with the bolt closed on it and in battery to test, I may try that tomorrow.

1911su16b870
09-10-2010, 8:57 PM
A good qualitative way to check your gas block installation is by applying air to the barrel (sans muzzle device) with the bolt closed in the upper receiver.

Josh3239
09-10-2010, 9:13 PM
An best way to see if everything is all lined up is to shoot it. The worst thing that can happen is it won't cycle. The thing isn't rocket science, you can do the adjusting at the range.

freonr22
09-10-2010, 9:15 PM
josh, you can rotate/reposition the gas block @ the range?

Josh3239
09-10-2010, 9:20 PM
Well, I suppose if it is pinned that can be problematic. Set screws or clamps can be easily adjusted. The gas block assembly is really hard to screw up, you have a far better chance of making a mistake on the fire control group than on the gas block assembly. But if it is pinned on incorreclty, I think you have bigger problems. If it isn't pinned, just get them reasonable tight to test it and once you found the sweet spot you can loctite them and tighten them up the appropriate amount.

mr2.0
09-10-2010, 11:40 PM
An best way to see if everything is all lined up is to shoot it. The worst thing that can happen is it won't cycle. The thing isn't rocket science, you can do the adjusting at the range.

wow!!! I expect a better answer than that especially from you, Josh.

mr2.0
09-10-2010, 11:46 PM
Here you go Falstaff, I made this tool like 2-3 yrs ago

Just came up with a tool to align the gas ports to perfectly to each other
http://i27.photobucket.com/albums/c194/nguyejp1/CIMG0866.jpg
Top piece is the screw hook from Home Depot, Bottom one is the result after an hour of filing
http://i27.photobucket.com/albums/c194/nguyejp1/CIMG0867.jpg
Differ angles
http://i27.photobucket.com/albums/c194/nguyejp1/CIMG0868.jpg
The tool is just small enough to go into the hole where the gas rod go into gas block
http://i27.photobucket.com/albums/c194/nguyejp1/CIMG0869.jpg
In this pic, you can see the head of the tool just stick out long enough from the gas block gas port to allow me align both gas port perfectly, What do you think? I feel much better now that knowing the ports are 100% aligned.

neal0124
09-11-2010, 10:36 AM
I did the same thing as above but I only used a piece of a metal clothes hanger.

Falstaff
09-12-2010, 8:47 AM
Thanks Mr 2.0! That's another great idea, the collective wisdom of this forum is awesome!