I have a friend that bought a used 45-70 who is having trouble with his hand loaded bullets keyholing at 50 yd. I offered to ask you folks what might cause this? The gun was build on a Mauser 98 action and has a 20" barrel. My friend casts his own bullets for this cartridge and is loading a 405 grain Lead Round Nose. If you have any thoughts on what might cause his bullets to be keyholing please let us know.