How long is the barrel on the rifle you were using? I am a little surprised that the accuracy is not better. I think the Pinnacle is similar in chemistry to the Black Mag'3 (both ascorbic acid based powders I think) and the Black Mag'3 seems to like heavy bullets although I believe it takes a long barrel to get the velocity due to the slower pressure rise rate compared to "hot" powders like Triple Seven that start with a sharp initial blast and high pressure spike. I have done most of my comparisons with my Omega which has a longer barrel than some of the other rifles. Black Mag'3 works great with 300gr. sabot/bullet combinations and 348gr. Powerbelts. The only heavy bullets I have in .50cal are the 348gr. Powerbelts. I have a mold coming from Lee to cast heavier conicals of a sort. If it gets here soon I may be able to start wringing out those bullets and powder also. My big problem is I have a small retirement business making lubricants for Bicycles and smokeless firearms and finding time to shoot has become a problem as my lubricant business has become more than part time. I am also curious as to how you can shoot a .458 bullet in a sabot. The largest bullet I can cram down my Omega barrel is a .451 and I have to go to a Harvester sabot to get those to load.