Round ball is the lightest projectile you can go without putting a hollow into it. If something with the smallest possible inertia is shifting under recoil, I dare say the issue is with an imperfection in the chamber rather than the swaging of the ball.
I have been using the Powder Inc loader for twelve years for my snubbies and it works great. I shoot Pietta 60 Armies and started with the 451 ball and shoot a lot in CAS and now shoot 454’s in the same guns. The 451 ring now is not noticeable anymore and the 454 leaves a nice ring. My Uberti pistols have always shot 454 and the Pietta 451. When I load the 7 1/2 Armies I just use a stand that works just fine. I prefer Pietta now and can’t see the difference other than Uberti charges more for their guns.