Gas Gun Question

i would agree it could very well be the steel casings. with the russian ammo, usually the newer polymer coated steel cases function fairly well, while the laquer coated stuff is alot more fussy.
 
Jay Cutright said:
Ok,
I cleaned the rifle and checked to be sure the gas system is open. The carrier will not lock to the rear after the last shot on either of two mags I tried & it stove pipes every shot using the TULAMMO.
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Is the failure to lock with the full power or the suspect (Tul) ammo? If it is with the full power, something else is going on.
 
It was just the Russian junk, it chronigraphed @ 2900 fps.
I lubed some of the cases and they still wouldn't function. I talked the guy into selling what he had to buy something with a brass case. This was easy after explaining I was going to have to tear the rifle down, polish the chamber, drill the gas ports and replace the buffer to maybe make it function with a steel case. If it was just a matter of a reduced load it would have been a little different but I think it was a combination of that and the steel case and since I didn't take the time to handload some light loads today with a brass case I guess I'll never know for sure.

Thanks for the help...jay cutright
 
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Selling the ammo was the correct solution. You could have fought that rifle for a long time to make it run with the Tul and risked problems with other ammunition.
 
Herzo said:
I built a 16" AR some years ago that gave me fits with extraction. Frequently, the bolt would not unlock, other times it would leave the expended cartridge in the chamber while the bolt would move rearward.
After playing with various buffer weights and beefing up the extractor spring, I finally determined that the gas port was too LARGE. . The bolt was beginning to extract before the cartridge case had relaxed. By reducing the size of the gas port, the problem went away. IIRC, the barrel manufacturer had drilled a 0.093" gas port in the barrel and I reduced it to 0.071" thereby reducing the gas flow to the bolt and delaying the time when the bolt began to move.
I am not saying that you may not have a problem with a blocked port, but I am saying that you need to be careful that you don't go oversize and upset the balance of the system.
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How did you reduce the size of the gas port? Is this some magic drill bit that puts metal back? ;>) I really wanna know how you did it!
 
kevindsingleton said:
How did you reduce the size of the gas port? Is this some magic drill bit that puts metal back? ;>) I really wanna know how you did it!
Click to expand...

I removed the front sight assembly and drilled the gas port out with a #21 drill being careful not to break through to the bore. IIRC, I left about 0.100" between the bottom of the drill and the bore.
Then using a bottoming tap, I tapped the hole with a #10-32 tap.
I installed a stainless steel #10-32 X 1/2" long set screw into the tapped hole - I don't know how much torque I put on it, but it was substantial. I had also blunted the end of the screw to get maximum thread engagement. The screw was long enough that the hex socket was above the outside diameter of the barrel when I installed it.
I drilled the set screw through to the bore for the appropriate gas port size (0.071" IIRC).
I then cut and filed the screw flush with the outside diameter of the barrel and re-installed the front sight assembly.
The front sight assembly traps the screw and prevents it from backing out.

I figured that I had nothing to lose and was willing to trash the barrel if it didn't work.
 
Herzo said:
I removed the front sight assembly and drilled the gas port out with a #21 drill being careful not to break through to the bore. IIRC, I left about 0.100" between the bottom of the drill and the bore.
Then using a bottoming tap, I tapped the hole with a #10-32 tap.
I installed a stainless steel #10-32 X 1/2" long set screw into the tapped hole - I don't know how much torque I put on it, but it was substantial. I had also blunted the end of the screw to get maximum thread engagement. The screw was long enough that the hex socket was above the outside diameter of the barrel when I installed it.
I drilled the set screw through to the bore for the appropriate gas port size (0.071" IIRC).
I then cut and filed the screw flush with the outside diameter of the barrel and re-installed the front sight assembly.
The front sight assembly traps the screw and prevents it from backing out.

I figured that I had nothing to lose and was willing to trash the barrel if it didn't work.
Click to expand...

Very cool! That's a great solution to the problem.

Thanks for the info.
 
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