Does your chamber dictate the 2.55" cartridge length or can you seat them out further? I usually seat to the maximum allowed by the chamber and typically load around 66 gr of Swiss 1-1/2 with 500-540 gr bullets and .060 wads. If using Goex, I've used up to 70 gr with more compression. Can you post a pic of the bullet? It sounds like it has a short nose with lots of lube grooves typical of some desIgns intended for smokeless powder. Nothing wrong with seating out further exposing lube grooves if the chamber allows it.
