I use standard primers in my .45/90, and cast my own bullets from a Lee 500gn 3R mould.
I was using 88gns of 2F and compressing a fair bit after drop tubing to get the bullet in, I never measured it but it would be more than .30". Used a homemade lube consisting of beeswax, neatsfoot oil and soap. The bullet was seated into the case with a die but never crimped, and I didn't resize any brass after firing. My Chiappa Sharps would group around 2" at 100yds with this load, but I had to run a wet wipe down the barrel between shots.
I haven't reloaded for the Sharps in over a year but when I find the time to get back into it, I'd like to back the powder charge off to about 80gns or so and run a cookie. I was always envious of the guys who could fire shot after shot without cleaning.
I wouldn't sweat over the primer issue too much, just experiment with a few different loads until you find something that works. The game I used to shoot called for a rifle that would deliver about Moa to be truly competitive. All the top shooters had rifles that were capable of that, and while a lot were custom rigs, quite a few were just italian repro's shooting the right load. These days I just shoot single action long range with the big sticks, a lot less frustrating!