The "Snicker Bar" measure was from a person who built large, early guns. If you build something later and smaller/thinner, it is a bit unrealistic. On the original rifles, the patchbox length and depth is all over the place. The later patchboxes are little more than decorative and can only hold a few cut patches. The earlier ones tended to be more "Snicker Bar" size. My personal opinion is that the patch box should be proportional to the butt stock. The length and width is going to be based on the patchbox design and the length and and height of the butt stock. The golden mean can be applied here for some guidance. The overall patchbox length is 2/3 the length of the comb. The patchbox door or box length is roughly 2/3 the overall patchbox length. The width is going to be similarly proportional to the patchbox design and the height of the butt stock from the butt piece heel extension to the toe and must be inside any toe moulding. Usually, the door is 1" to 1 1/4" with the box being about an 1/8" smaller than that. As to the depth of the box, I make mine a little over 1/2 the width of the butt stock at the widest point. Usually that works out to be between 3/4" to 1".
