Since you have the 20" barrel and are shooting the 100-115 GR bullets, the H335, H322, RE10x, X-Terminator will be the best choices.
27.5 GR. And work your way up.What would be a good starting load for RL 7 and Speer 90 gr TNT. I have a 16" SS barrel but it is a 1:9 twist with a SAAMI chamber. I know guys are having good luck with 29.5 so I was thinking of starting with 28 grs and working up to it.
Rhett in Az