I have finally been able to gather all I need to load for my .577/500 No.2 BPE. I am new to the double rifle world but have been reloading for 50 years or so with both smokeless and black powder. Is it necessary to resize the case each time on a double rifle when both barrel fired cases interchange? I understand this is more of a plains game rifle. I have done some tinkering at 25 yards and have both barrels shooting at POA. This is an 1875 T. Turner hammer double. What range would these type of rifle be regulated to? I'm shooting 340 grain cast over 145 grains of black powder with .062 card, and 1 lubed wad over the powder.

thanks