Gas port on the Shorty Norks. How big?

Grizz Axxemann

Grizz Axxemann

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My Nork CHOPMOD is still slowly coming together. All the parts are ready for coating, stock is inlet, and then I just have to put it all together.

I remember some of the early CHOPMOD rifles having short stroking issues due to a lack of dwell time for the gas system with the shorter barrels or something like that. A few guys had to enlarge the port, but I can't find the thread for the life of me.

I measured my gas port on the barrel (since the barreled receiver is close at hand, while the rest isn't) and I got a .065" size. How big is the hole on the factory specced shortys, and anyone else who has a chopped rifle can chime in too.

I know I could do a little trial and error once everything is built, but it's easier to drill holes in things when it's still a pile of parts. No scuffed finish, no risk of jaw marks left behind, and nothing to remove, because there is nothing there.

This gun will be eating everything that fits in the chamber, so I want to make sure it's going to cycle properly.
 
I've built a few hundred shorties and never needed to change a gas port.
MustangFrank did modify his but not sure what size.
My GO TO rememdy for cranky shorties with out of synch dwell time was to slightly enlargen the inner volume of the gas plug.
Allowing the cylinder to accept more gas before pushing the piston. Worked like a charm in the many norinco rifles I've modded.
 
How big did you typically have to go, Thomas? Sounds like an easier fix than having to tear stuff apart repeatedly, provided that my rifle ends up being finicky.
 
I opened and deepened the gas plug cavity by about one to two thousands of an inch at a time until I got reliable feeding/function. Unfortunately I have no "magic number" to give as each one was different.
I'll add that I wouldn't "expect" a problem with a shorty as far as gas system mods go. The vast majority of them I've done have functioned just fine with unmodified factory parts. Just the odd finicky one warranted stepping outside the box.
 
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I have the same issues with my chopped barrel. I have not modified the gas port and was also searching for this answer as to how much to bore it out. I wish it was as easy as take a drill bit of ### size and drill out the port.

The gas plug enlargement makes sense but I don't know how to remove thousandths of an inch at a time without a lathe. So I guess I am stuck in single shot with the occasional double shot rifle until I figure out a way to do that at home.
 
Send mustangfrank a message, he is one person I do know personally that fixed his by enlarging his gas port. It was posted about a few years ago.
I have extensive notes at home on this subject but those are 5 hours away and weeks before I'm home again.

Rule out other culprits by ensuring optimum gas port alignment and observing piston drop with the oprod removed. If it doesn't drop with the appearance of some vacuum, could be a crappy piston. Also, many guys don't realize that the gas piston itself is hollow almost right to the tail end. A judiscious cleaning can often remedy apparent gas system issues.

With some of the shorties, the timing is just off slightly and issues can be solved at the gas system or sometimes at the recoil spring. I've seen rifles glitch up with a wolfe spring but run perfect with a GI or norinco spring. It's not always a simple thing.

I would recommend getting jerry kunhaussen's 30 cal service rifle shop manual from brownells. A real eye opener for diagnosing and remedying gas system related issues.

That's all I got for ya.
 
Nice response. I was meaning to switch back to the usgi spring and see how things went from there. I will exhaust all of the methods you mentioned before altering my rifle.

Sincerely thank you.
 
I just happened on this thread and will share my experience. In my analytical mind (after all other inspections came up negative for issues) I stopped being all scientific and tried to figure a way to provide the system with more gas to make it function properly since that is what drives the action. I do not remember the size of the drill bit I used and probably doesn't matter. The gas hole in the barrel was not allowing enough gas through in my gun. Could have been bumped with something or just undersized from the factory. Most people said don't do it but it seemed the only logical solution. I was prepared to replace the barrel if this somehow wrecked it.

You need a collection of bits with a lot of sizes so you can enlarge in very small increments. I just started with bits that fit easily and slowly worked my way up to the first size that was snug. I test fired after each enlargement until it functioned perfectly. I would think if it doesn't improve after two small increments, you should stop. Also comparing your gas port size to one that works will indicate if yours is out of spec. Only advice is test fire every time and don't go too far. You must check every other possible issue like action rubbing on something and everything else 45ACPKING said before taking the plunge. Good luck.
 
I would also add one more thing. The gun functioned just fine before getting the barrel shortened so it could have gotten bumped around the gas hole in the barrel in all the handling or needed a bigger hole in the barrel for the shorter barrel. It was not a factory shortie. That was my biggest clue. The bullet had left the shorter barrel before enough gas had been transferred to work the action properly. At least that's my theory.
 
My only other comment on this would be that I have chopmodded an honest couple hundred or so M305 and usgi M14 barrels, via dlask, and less than a handfull experienced any glitches. The vast majority of those were fellow CGN'ers rifles.... And issues should/would have been reported here forsure.
 
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