Strangely enough, one of my posts has managed to somehow make the first page on a google search for "homemade ammo". For anyone who is looking at that one, I thought I'd add a little something I've learned from reloading. If you're going to try reloading, my biggest piece of advice would be to start with 9mm ammo. Of the calibers I have done so far, 9mm is the only one so far that appears to be impossible to overload. I had thought that switching to a powder that would only need 5 grains of powder, as opposed to 7 grains, would leave more room in the cartridge. Instead, it turns out that the other powders just didn't pack as well and took up as much room. I also haven't been able to get remotely close to the minimum overall length specified for any max load I have used. The powder takes up so much space that the bullet just won't press down that far.
To put it simply, I have yet to press a bullet in far enough to risk high pressures, and the one time I "double loaded" a cartridge, I had a huge mess on my hands.