As some of you here know, I shoot a lot of cast bullets through my 10mm. I thought I'd share this info, hopefully it will help inspire some of you bullet casters out there. I recently ordered a mold from Mountain Molds for a heavy 10mm bullet, that has turned out pretty well. (You design your own bullet on the Mountain Molds website, then the mold is made to your specs.) This one is a 220gr flat nose, designed specifically for maximum case capacity, and at .673" long, is shorter than a 200gr XTP bullet. I had designed it as a 215gr bullet, but they end up at 220 with lube, probably due to alloy variations. I also designed it to work with 40 S&W brass, loaded to 1.260", since I have about 10 gallons of it. Most cast bullets can't be loaded to 1.260" in 40 S&W brass without exposing the lube groove. I'm still working on load development, but AA9 seems to be a really good candidate right now, pushing these over 1300 fps average from my compensated longslide. Penetration in dry cedar firewood is very impressive; I had to rebuild my backstop after firing a bunch of these. Edit: forgot to mention, the bullet on the left is a sized down .41 Mag bullet from a Mihec mold. It also weighs 220gr; you can see the difference in bullet length due to the design.