As has been said, some of the fast-burning smokeless powers are not very dense, i.e. they don't take up much space in the cartridge case. I throw twenty cases, check for consistent weight with a scale, throw twenty more, check, etc. When I have fifty or one-hundred charged cases, I then place the block containing the charged cases beneath a light and make certain that each case has the same powder level. I've been reloading since 1972 and have only had one "double-charge" with Bullseye powder. Had I not checked the level of the charged cases, I would have no doubt damaged a Model 10 revolver, and possibly injured myself.

Lastly, this should not be a problem, but if you encounter bullet deformation with the lead bullets or for that matter any bullet, you may wish to consider adding a step to your process....seat all your bullets to the desired depth, then in a final step, crimp them.

HTH.

JPJ