Re : Shim Kit
Don't shim the Gas Cylinder, try the 180deg trick first by flipping the gas lock to see if it times better (read the stickies above on how to do this). Tactical Teacher/Hungry is going to tell you "friends don't let friends shim the M14/305s". If that doesn't work, someone on here is bound to have a spare you can swap until you find one the times correctly. This is exactly what goes on at one of his clinics.
I thank you for those sentiments! Yeah, I have the shims here and I make them with a "tool and die maker made" punch set but frankly, at my clinics I ensure nobody ever has to use shims.... EVER!
Whenever I build or rebarrel with an American barrel (read: Krieger, Criterion, Douglas), I have a stable of TEN M1A gas cylinder locks to draw from. What I will do is trial fit (and the 180 degree flip trick) to ensure we obtain a super tight relationships (read: hand tight to 4 or 5 o'clock and rubber mallet to 6 o'clock) with the new barrels and gas cylinders. NO SHIMs, EVER!
If you really, really wanna send me $5 then by all means, mail away and I'll send you a set of shims, but I would rather we never used them.
I'm packing up right now for a Kingston/ Frontenac Rifle Pistol Gun Club M14 clinic this weekend and I will ensure I don't forget my set of THREE Norinco gas cylinder locks I use to let Norinco M14 owners trial fit on their M14 rifles. And that's why it's important you get to a clinic before yer #### falls off!

ha ha ha ha ha
Of course I'm just kidding about yer #### loss!
Now if you are in the Kingston area and have not got much going on this weekend, bring your M14 or M1A to the clinic for a tune up! All good times.... $50 for the day!
Okay, back to the thread of the OP... get your self a pair of castle nut pliers (or make them) and now you can access the area that affects accuracy a whole bunch!
Cheers and keep helping all them nooob out there!
Barney