I have a Savage 12 in 223 that will shoot .50 groups frequently with sierra bullets and will do .75 with hornady match and nosler match. But load a 60 gr nosler partition and crap is what you get, 1.75- 2.25 is as good as it'll do.Been trying to get my son-in-law to take them, but his Ruger twist to slow for a 60 gr bullet. My Savage 270 will not group better than 1.5 with Nosler ballistic tips but will do better than 1" with hornady sst's and gamekings. My point is ,you need to try more different brands of bullets before you start screwing arround with your beding or anything else.The number of .308 bullets available is huge. Also you only named two brands of powder, did you try less than maximum loads ! I've noticed my best groups tend to come from a canister with the Hodgdon name on the label. Also and this might be the most important, shoot you group with all first shot rounds( when hunting it's the first shot that counts) wait 20-30 mins between shots,and possiably run a patch thru your bore between them as well. You will likely be hunting with a clean barrel , so why not know where it's going to place the first shot. After the first one he will be running anyway,if you miss, and a tight group will not help much then.