Lodraw,I have'nt used the XTP bullets.But I have used W231 with 230 Winchester JHP for some pinloads.My Speer #11 manual shows 6.2 gr of W231 as max load for 230 ball.I have used this load.In brass cases I get a slight flattening of primer.Using +P Remington cases I get no signs of excess pressure.I load to 1.225",using Win.LP primers.Loads averaged 908 fps shot through 5" Kart NM barrel.Interestingly the same batch shot with my Baer PII averaged 26 fps less.
I think AA#5 powder would be a better choice.I have seen data that suggests higher velocity with lower pressures.I plan on working up some loads using this powder.