It's a good quality part and I like being able to fit it to the gun for close tolerances. I think having the bottom more square is best suited to the higher pressure and heavy loads. I did some experimenting with a 9mm with the square bottom and found that my split times between shots went up with the square bottom. The square bottom isn't needed for the little 9mm. For the 10mm and 38 Super, I would give it a try. Even if you go back to rounding the bottom, it's still a good quality part.