yakipreacher,
If you want to check the diameter you need for your rifle with an odd number (3, 5, whatever) of grooves...
Use something to increase the diameter of the skirt on a minie. Like sit the tail on a ball bearing or something and hit it on the nose with a hammer. Then, while holding the nose with a good gripping set of channel locks or pair of pliers, very carefully use the rifling at the bore to machine down the outside diameter of the minie skirt. Then the minie skirt can be measured with micrometers. After repeating the process a few times a set of figures can be developed to indicate the diameter.
If the bore is just really really bigger than mold manufacturers felt like making molds for there's still hope.
Options #1. You can lap out the diameter on your molds. Or, there's Erik Ohlen in Corvallis, Oregon. He has increased the band diameter on a 58 and 69 minies for me to have them drop out at precisely the desired size. He is very good.
Options #2. You can add a little paper. In days gone by it has been reported on the forum about putting one single layer of tissue paper around a previously lubed minie with good results. I've never had the bore to try it in but considering the brilliance of such a simple solution (so obvious in hindsight!) I keep the knowledge filed away between my ears in case the occasion arises. Another way of adding paper is to paper patch the minie (wrapped wet and let it shrink on with drying), then size to fit the bore. It's a lot easier than it sounds. Another is to have the minie undersized and dry wrap with a single layer of paper at loading, folding the extra paper up into the hollow base to keep the paper from slipping off the bullet as it travels down the bore to rest upon the powder charge.
There's another option that I'm surprised no one seems to use... a pound swage. Pound swages were really common in the 1800's as the way to make bullets fit your gun.
Hope you get to make lots of elk sausage!