bfr 45-70
Hi there. I've got a couple of them. I have had that same problem with cirtain factory ammunition. I couple of low pressure commercial cartridges I've used in mine tend too leave more than dirty carbon soot. They leave unburned, or partially unburned kernels of powder around the mouth of the case. When I extract the case, it tends to drag some of these back into the cylinder on the case's way out, as we know, b.f.rs are proud of tight tolerance, and the 45-70 is not a fully straight-walled cartridge, its slightly conical in design, unlike a .45 colt or similar true straight-walled case. The kernels are bulky enough to prevent the newly loaded cartridge from moving fully forward. The resistance in cycling is the rear of the case hitting areas of the recoil shield and loading gate. This is especially a p.i.a. If debris of this sort fills the small case rim rebate area at the heel of the cartridge. My solution was to move exclusively to "class II" or class III cartridges on either my handling, or factory ammunition to ensure higher case pressure, and a hot, and efficient powder burn. Its unfortunate, but the 45-70's case size doesn't lend itself well to downloading. And the b.f.r. Does not lend itself well to firing "dirty" ammo....or powder leftovers.