So I'm getting the feeling that the more important dimension is the width , so you don't hit the side barrel ,correct ? But different lengths will work , some better than others I suppose . What about bevel up or down ? I'm guessing bevel up would be better for a longer flint . Thanks for the help so far guy's , I just never had to deal with these kind of circumstances when choosing what primer to use in a load , or what cap on my percussion gun's . LOL .