.44-77 PP bullets.

[Nuclearcricket]

If you are careful, you can get away with spacing your holes on 3/4" centers, if you can make a bigger box 1" centers will work well. A simple way of figuring hole spacing that has worked out pretty well for me is to divide the length of your part by 2 more than the number of holes you need. If you want 10 equally spaced holes, divide the length of the part by 12. That will give you the location of the first hole and the space between the holes. Yes I know at first blush it doesn't make any sense but what it does is to put the center of the hole #1 at the edge of the part, you just don't drill that hole. Also the same with the last hole #12 that you don't drill either.
Sam