Ive been shooting the factory recomended load 90- 130 gr pyro P load data that came with this white gun,its been great over the years. Started shooting it in my encore as well, needed some pillar studs from TC for the gun.they asked what loads i was shooting out of it and i told them same as my white rifle Pyro P and the guy had a shit fit.told never shoot nothing smaller than 2F in any of there 50cal guns. Is there that much of difference in psi in the two?!. I just purchased new mountaineer is it ok to shoot 3f P or 777 3f in this gun? I have 2 lbs of it left over,like to use it before going over to bh209. Rob.
The finer powder may burn/flash faster. Unless you are right at the upper end of a max load I wouldn't be concerned. You could always back the charge to leave some daylight at the top end, you would be fine. Pyrodex is also a fair amount weaker per charge compared to the same amount of 777 or B209. I'd back below top end levels & continue on. I would switch to B209 when you are out.