I'm fairly new to reloading but my 45 and 40 reloads are working great so far. I'm loading my 10mm pretty hot, cause that's the point of a 10mm, but they aren't as hot as the factory ammo from Underwood. I'm putting 9 grains of IMR 700x with 165 grain bullets. Anyway, when I shoot them the end of the brass separates right around the base of the bullet. So I wind up with a little ring of brass at the end of the chamber that comes out easily with a cleaning brush. I reloaded some nickle plated casings and they aren't doing this. Most of the brass is from Underwood. I think the nickle plated are Remington. Someone suggested my bullets may be seated too deep but the OAL is just a hair under the length of the Underwood ammo. The powder is quite full in the casing so I'm wondering if a couple grains are getting between the bullet and the casing. Any ideas?