Stock needs to be fit correctly?

Bush Hunter

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Well I bought some norinco 7.62mm for my M305. I cut down, threaded and target crowned the barrel. I installed a USGI fiberglass stock. I fit the the stock. It fuction checks A/OK. This ammo fails to feed 95% of the time. It is very accurate though so Im very happy in the regard. I have 168g SMK hand loads that feed every time I fire the rifle. It is lubed correctly ect. ect. and the gas system is shimmed and clean. Could this be a stock issue still? It has a norc spring and a S&J match op rod guide. I have also tried a wolff op rod spring but with the same results. Any ideas? Any idea where I could get this checked in Alberta or B.C?

Cheers, BH
 
A handful of guys have had issues with the norc ammo in their socom II and chinese short rifles. 1 fellow very slightly enlarged his gas port on the barrel and reported it solved the issue. He tried "everything and every mod" known and nothing solved the problem. It now apparently functions fine will all ammo.
That said, I highly recommend AGAINST this procedure unless you are skilled on the tools that allow it to be done right :D
Otherwise, use the ammo she likes and leave her be ;)
 
Thanks for the replys. One more question. What about shimming the plug to increase dwell time? Or would I have to shorten the plug? I am a machinist and millwright so I have access to the correct tooling to do either job.
Thanks B.H.
 
Got it figured out. Need to shorten the mating surface on the plug a touch at a time(.001"). Will be a little harder on the rifle guts but with the Wolff spring it should help. Now to find a spare gas plug.....
Any thoughts on this?
Cheers, B.H.
 
I would advise honing the inside of the gas plug over removing material from the piston/plug contact area. This will create more volume and increase gas pressure behind the piston
 
I would advise honing the inside of the gas plug over removing material from the piston/plug contact area. This will create more volume and increase gas pressure behind the piston

If I shimmed the gas plug out would this not do the same? Bit at a time of course. Thanks for the heads up and all of the great info From prior posts.
 
Try different ammo first. I found that the Norinco ammo was the cause of that type of failure in my rifle, but no where near as bad as you mentioned. Norc gas parts float around on EE often enough. Once you pick up a spare, then start screwing around with it.
 
If I shimmed the gas plug out would this not do the same? Bit at a time of course. Thanks for the heads up and all of the great info From prior posts.

Short answer about shimming the plug... No, do not do this.
The only accepted ways to increase gas volume are:
1) to adjust piston dwell time at the piston/oprod interface. This is done by 4 jaw chucking the piston in the lathe and shaving the tail end only. The tail is the solid end that contacts the oprod.
2) By honing the gas plug to increase it's volume. (The SEI socom gas plug is an example of this in action)

Other than that, there is nothing that can be done that will not cause other problems.
Examples:
Shimming plug or, shaving top end of piston, allows piston to travel to high, changing port alignment and timing. Cycling issues will be a result.
Shaving gas lock thickness below designed minimum- same problem being created with negative port alignment/timing
And finally, shimming gas plug or shaving top of piston, can lead to insufficient piston protrusion from the cylinder and only so much can be shave from the cylinders piston tail opening. If the piston tail end hangs up in that opening during the firing cycle it can lead to a violent cylinder rupture.
If it were me, I'd find a smith enterprise SOCOM gas plug and measure it's depth and diameter and replicate that in a chinese plug.
My guess is it will only take a hair more volume in the chinese plug to get some rifles cycling all ammo. Just my guess tho.
 
Thanks for the great info. Honing will be alot easier then trying to cut tiny shims or Machining the piston tang(that would be pretty easy to so I might do this all well to make sure my dwell is correct). I will do it it in small amount to start and let you know how it turns out. I will enquire about the socom plug I.D. for a base line.
Thanks, B.H.
P.S. APC King, do you still do trigger work?
 
Do a search on M14forum or google for M14 piston dwell timing.
Articles by Art Luppino are must reads before deciding on or performing piston mods. Gus Fischer is also an excellent resource for gas system info in general. Mind you, they are discussing mods to US dimension parts, but the principles behind the subject are the same.
 
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