Thank you for your question Big Bore. I have had no issues with my PC bullets in my 45-70 Marlin. The bore is easily cleaned with a couple of swipes. Of course the bullet base gets powder coated too, so it kinda acts like a gas check.
Unless you are pushing a light 45-70 bullet to 2000 fps or better, I might switch out to factory ammo, but why? At 1600 fps with a quality powder coat, I think the mostly only limiting factor is recoil. At 1600 fps recoil is manageable, but when I pushed my 340 RNFP bullet past that with more powder, the recoil became punishing.
Okay, accuracy is very good too. I switched out the OEM buckhorn sights to the superior XS picatinny rail & sight set. Way better there. Good accuracy, no tumbling & nice groups....