All I did to my Stevens 223 was to stone the burrs off of the trigger parts and that's it. I haven't done diddly squat to the stock or anything else. Spend more time on different loads for your rifle. Mine hated all the factory ammo I had tried. Shot some of it to over 2" at 100 yds.
When load developing for it, I found it liked to be slightly less than "max" according to the manual.
This is my trigger-stoned-but-all-else-stock-rifle, shooting it's favorite handload:
That's 5 shots, from a cold, clean barrel at 100 yards. It will regularly repeat that feat also. And that's measured "outside to outside", not "center to center".
The "load" for mine is 25.5 grs of old surplus BL-C2, in Rem brass, with Rem 7 1/2 primers and Hornady 50 gr Vmax bullets.
That load is not "max", if I bump the powder charge up, the group opens up.
Try some different loads...