Some things to look for:
-Oil on the latch.... as stated, is a problem.
-Side to side play when the barrel is locked up.
-Large gap between the breach and barrel, hold it up the a bright light...
-Loose scope mounts and or rail. Put a very small dab of Super Glue on the screw threads of the scope rail.
-You may just have a rough bore. Flitz the hell out of it (all the while being careful of course..)
-The butstock bolt may be loose..
-Odd pressure point in the forearm.. going out on a limb there

The FAQs really are awesome and have tons of hours dedicated to it all.
These are just a few things to look for. My 223 was a P.I.T.A untill I broke it in...now it's one of my very best shooting rifles, I love it.
-Aaron