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Welding gas port

Rapidrob

Plastic
Joined
Jul 30, 2015
I have a .223 caliber semi auto rifle that has a too large gas port. The gas port is 14" from the chamber. Listed gas port pressure is 18,000 PSI. Can I safely weld in the gas port and re-drill it to the smaller gas port size? The weld would be small and only take a second or two to fill in with a MIG.
Thanks for any info.
 
I have a .223 caliber semi auto rifle that has a too large gas port. The gas port is 14" from the chamber. Listed gas port pressure is 18,000 PSI. Can I safely weld in the gas port and re-drill it to the smaller gas port size? The weld would be small and only take a second or two to fill in with a MIG.
Thanks for any info.
you will distort the inside of the barrel and it will never shoot worth a damn again. FIrst things first, how much oversized is the hole? Next, is it causing any problems? Generally overgassing does not cause problems unless its really severe.
If its an AR, first try an adjustable gas block for the easy button. If you absolutely need to close up the hole, id drill it for a set screw, not all the way through to the bore, but enough to catch 4 threads of a 6-48 or 8-40 screw. Id then install a set screw with red Loctite, drill the proper hole through it, and file the outer contour to match the barrel.
 
Most setscrews are case hardened or through hardened, so it might be hard to file. You could try it first holding a setscrew in the vise. I've destroyed many carbide inserts boring collars when I forgot to remove setscrews from them, they are substantially hard.

If the setscrew is through hardened you might heat it to a red heat and drop it in lime to anneal it first.

My own experience with case hardened parts is that annealing is a hit or miss operation.

It would only take a few minutes to make a threaded plug out of 4142, which is about 28RC. I'd drill the hole down the center while in the lathe and cut it part way off the rod so it can be broken off after it's screwed in tight, then whatever is sticking out could be files easily enough. It'd be interesting though to make a stainless taper pointed screw to use as a gas adjusting screw, though there may not be convenient room block for a screw head to adjust.
 
Most setscrews are case hardened or through hardened, so it might be hard to file. You could try it first holding a setscrew in the vise. I've destroyed many carbide inserts boring collars when I forgot to remove setscrews from them, they are substantially hard.

If the setscrew is through hardened you might heat it to a red heat and drop it in lime to anneal it first.

My own experience with case hardened parts is that annealing is a hit or miss operation.

If hardness is a problem, just use an 18-8/304/316 stailness set screw, they will never be hardened beyond any cold work from making them.
 
Depending on how oversize the port is, you might be able to swage the port smaller by putting a 1/2" ball bearing on the port and leaning on it with an arbor press. It will likely require a lot of leaning. Try to refrain from using a hammer.
 
Can you enlarge the hole in the barrel or gas block and fit a bushing with a smaller hole? Mini 14 uses a bushing between the barrel and gas block. On my son's rifle we had to play around with different bushing IDs to get it to function the way he wanted.
 
Closing the hole with a ball bearing or drilling and tapping for a set screw are both good choices IMO. However I would prefer to go smaller than a #6 screw. I would be looking for more threads per inch in that thin wall thickness. I don't care for the welding idea. I suppose I am afraid of damaging the bore as well as changing the structure or hardness of the steel.
 
I've been thinking about GeneT's suggestion for my own rifle, the only price I saw was about $40. Considering that the wall of that eccentric tube is pretty thin I find that price to be acceptable, though they may be modifying high volume purchased gas keys and modifying them.
This would give the best of all worlds short of going to an expensive piston system to keep the upper clean.
 








 
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