looking at what type of velocities you are getting shooting 3 50gr. pellets out of a 26 inch barrel using the 209 for ignition and a 175 gr bullet out of the 45cal. had a 3 shot group yesterday inside a 1.5 inch bull at 100
I'm getting 2000 fps out of a .50 290gr. Barnes spitfire TMZ using Black Mag 3 115 gr. Seems like you should be getting more using a 175. However, I think the sabot may start to give up before you get much over 2000 fps. MMP makes a magnum sabot that may help you get over the hump.