Cycling Prob. With Shorty

[doubletap]

Have a STG-58 I built up as a 17" on an Imbel. It has been a continual problem to keep it cycling. The other day was out with some Argentine and had to run at 1 to keep it going, and then experienced a couple of short cycles to boot.
I have opened the port size to .120"=/- a couple of thou. I have also removed the gas block to completely clean it so I know the port and block are not obstructed.
The big question is: Should I replace the block with a Tapco NIB one? Are they drilled for the pin already? Should I just say hell with it and silver solder down the one I have? Trading out gas plugs with known good ones doesn't make any difference, so I am concentrating on the block.
Hints, ideas, all are welcome.

Doubletap

Oh yes, this one has a plain muzzle, no brake on it.

[FootLongCuban]

Try swapping the gas piston. If all else fails you can always buy a brand new barrel with gas block from CDNN ($99).

[W.E.G.]

One quick test would be to just put some Permatex or teflon tape on the threads of the gas tube. It should hold for at least a magazine or two. That should tell you whether a gas leak at the threads is the issue. If that is the problem, then you can solder or replace as you see fit.

[doubletap]

Oopps! I should have also mentioned that this has the short gas tube brazed in place ane, yes, the gas tube pin is there too.
Have tried several different gas pistons as well, no difference.
The reason I am so suspect of the block is that it came off really easy once the pin was driven out. Had expected it to be in place with a tighter fit.
Is it OK to silver solder the block in place? Would that offer a decent chance to seal any leak between barrel and block?

Thanks again for the answers provided.

Doubletap

[W.E.G.]

I've never heard of soldering the gas block.

The fact that it may have been NECESSARY to braze the tube is an indication that the gas block and/or the gas tube may have high miles.

I think your proposition to try a different gas block makes sense. Especially since you say yours will come off easily. I've never tried to remove a gas block. But, I always envisioned a negotiating a very tight fit while treading a fine line between repair and destruction in the event that I may have to attempt a gas block job at some point.

Of course you will need a different gas tube too. I strongly recommend the full-length tube.

[whatnow]

If everything with the gas system looks good,
sounds like the gas port is too small. Forgot
the # for the drill bit to use, maybe someone
could help out.

Bill

[Jayson at IGF]

Usually a .120 gas port is enough to get one to function. Does your gas piston move freely back without the spring in place. Seems to me the shorter gas tubes are more prone to bind the piston. Some of the short gas tubes are pulled over to one side due to the solder cooling and slightly warping the gas tube.

After that I would check the bolt carrier and make sure it moves back and forth freely in the receiver.

Finally if you havent done it before I would suggest that you take your stock off and give the recoil spring and recoil tube a good cleaning. After that use some oil in there a good teflon based or some sort of synthetic will do the job.

Good Luck

[W.E.G.]

Originally posted by Jayson at Investment Grade Firearms:
<STRONG>...Seems to me the shorter gas tubes are more prone to bind the piston. Some of the short gas tubes are pulled over to one side due to the solder cooling and slightly warping the gas tube...</STRONG>

I've noticed that condition in the short tubes also.

Other than for the purpose of keeping the gun "correct," I see zero advantage and considerable disadvantage in the short tube with obsessive gun-cleaning bunch around these parts. I recommend the long tube for ALL recreational applications.

There may be some small merit in the short tube in conditions of extreme exposure to debris/moisture.