I'm new to this caliber and I'm struggling to find accuracy. My rifle will group tight but only after the barrel is hot. The first few rounds are all over the place. I have tried three powders so far, two ladder tests and one Ken Waters Pet load. My ladder tests were run with Varget and IMR 4064 with 120g Vmax and 139g SST. The Ken Waters pet load was with 139g SST and 748. So far Ken was the closest!I got just over a 2" group at 100yrds on a cold barrel and .5" group on a smoking hot barrel. The barrel has about 150rounds down it so far. I have purchased 162g ELD-X to try. My thought process is that this rifle might like heavy bullets. The rifle is a Ruger American, and before the RA bashing starts, I own 7 Ruger Americans and all shoot sub MOA on my hand loads at 100yrds so I'm not going to entertain that the rifle is at fault at this point. I really think I just havent tried the right powder yet. I have access to about any powder that there is except H4350. Suggestions?