To make it reliable: clean it fully...then grease the specific points that require greasing (don't just grease everything, look up the info as to which specific places to grease).
It's reasonably good accuracy right out of the box. First time I brought my BONE STOCK M-14 to the range, with the sole intention of zeroing the iron sights...at the end of the day I took aim at a 12" square steel gong. 17 hits out of 20 shots. Now, that might not sound impressive...but consider:
-heavy gritty trigger pull
-just finished a "rough" zero, using iron sight adjustments I wasn't yet fully familiar with
-original Chinese iron sights...which can sometimes be a weak link (serious iron sight shooters replace these)
-stock original spring guide (replacing these with "national match" or "round" spring guide helps a lot)
-original Chinese plastic stock (not the best for accuracy)
-cheap-ass "budget" ammo known as MFS
-unfamiliar with the rifle at that point
-fake "flash hider" that had no cut slots...so while the bullet is in free flight, the muzzle blast is still contained in 3 inches of "can"! Pretty poor for accuracy, replaced a week later with a proper FH (thanks Doc!)
So we replaced the flash hider with a proper one with vent cuts, I cleaned up the trigger, I replaced the iron sights with Springfield NM units (too expensive, but I wanted them and still like them!). Then we TIG welded the gas system (like NM modifications done for old US Army shooting teams, and the M-21 sniper system, and M-14 clinics).
-same stock
-same crappy spring guide
-same cheap-ass "budget" ammo known as MFS
Had to re-zero it again...new iron sight components installed you see...I messed up part of the procedure for tightening the rear drum. Might have been one or two clicks "off" of my rough zero.
Result? 20 rounds, 20 solid hits, rapid fire, 200m
No, it's not the same thing as saying "uh, 1.5 MOA", because frankly I've not had the time or money to have done any more shooting with it, changed careers and provinces! But, this is four magazines worth in about a minute or so, hitting a square steel plate using iron sights, 200m, with budget ammo.
Could I improve upon that? Absolutely:
-do a full proper extensive zero
-experiment with many brands of .308 ammo (but not the heavy boolets, they just wreck things!)
-install the spring guide I bought today ($35 from TSE, this one is fluted for lighter weight)
-buy a better stock and bed it, or buy an expensive stock that doesn't need bedding (JAE, most of the aluminum based stocks)
-read up on other accurizing modifications I'm not yet aware of