For tips on how to inspect, maintain, repair, and modify your Chinese M14,
check out the posting at;
http://www.m14.ca/seminar/M14_Seminar_EBR.pdf
A US GI fiberglass stock installed on your Chinese M14 will generally give better groups than the CHU wood stocked rifles ... but some CHU wood stocks shoot surprisingly well ... at least until the soft CHU wood compresses and the stock to receiver fit loosens up.
The GI glass stocks will also last longed, and change less with different weather conditions.
If you put a GI stock on a commercial M1A/M14, you have to pad inside the stock to block the shorter op rod pin from walking out during firing, and causing a mis-feed.
I have several different M14 stocks that I swap back and forth on my three test Chinese M14 rifles, and also three of the latest versions of our
prototype ALUMINUM M14 EBR stocks.
Just to give you a sample of what might happen at 100 yds,
here are my results from the last few range sessions;
I used the same ammo
[inexpensive Federal 150 Gr Powershock SP / Blue box ... which shoots better than PRVI in all the M14 type rifles I've tried it in ]
same rifle [ receiver and 22" barrel with standard flash hider installed ]
forearm resting on bags OR bipod,
10X scope
changing around to different stocks, with 10 rds fired at 25 yds to find the new zero [ which WILL change when you swap stocks ] and to help settle the action into the stock before 100 yd testing;
1.]
BLACK PLASTIC CHINESE stock # 1, [ these plastic stocks have a metal insert just like the wood stocks ] Harris Bipod mounted at forearm ... 5 shots - 1 1/2" @ 100 yds.
[ 4 out of the five were into 3/4" ]. This surprised me because I was not expecting decent accuracy out of the plastic Chinese stocks.]
2.]
OLD/SOFT [ like balsa wood? ] CHU wood stock rested on sand bags at forearm ...
5 shots - 2" @ 100 yds., which is again surprisingly good.
3.]
US GI Fiberglass stock # 1, very tight fit, as new at rear of lug bedding area,
Harris Bipod mounted at forearm ...
5 shots - 1 1/4"
[ 4 out of five into 5/8" ]
4.]
US GI Fiberglass stock # 2, slight bit of longditudinal play, rear of lug bedding surfaces slightly worn, rested on sand bags at forearm ... 5 shots - 2"
[ 4 out of five were at 1" ] ... not sure if this was the bags or the stock??
5.]
BLACK PLASTIC CHINESE stock # 2, rested on sand bags at forearm,
5 shots - 3" [ not sure what happened here .... one of the stock screws was installed at an angle/cross threaded?? ]
Bottom line, stock fit will have some effect on accuracy, but I suspect the big difference for me, is that I shoot more consistently off of a bipod than I do off of sand bags.
YPMMV PS: every time you swap stocks, or even take your M14 out of the stock for cleaning, after reassembly always test for hammer follow BEFORE loading any ammo.
Good luck with chasing after accuracy with your Chinese M14 ... it can be both challenging and rewarding. The best advice I can give you, is spend your money on finding out which brand and type of ammo your 14 likes best, BEFORE spending money on accurising.
TTFN
LAZ 1
[;) 
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Accuracy Norinco M305 
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