Machinists, a little help pls.
 

O.K. from a different web site I was encouraged to buy 444 marlin brass for my new .410 shogun. The primed brass does not fire.

When .5 mm is ground off the base of the brass it will fire the primer.

O.K. I won't embarrass myself by showing the job I did grinding off the .5 mm, just say it was not even at all. Even though I find it hard to believe that a $200 shotgun would have those kind of tolerances yet here we are. What is the best way to take a bit off each brass hull so that they are flat on the bottom and down by .5 mms and all the same? I don't have a metal lathe.

A sheet of glass, with a medium grit emery/sand paper, and lots of elbow grease. Or possibly draw filing it. It's an option, but prob not the best.
Mark

Ps .5mm is 0.0196". That's almost 20 thousands of an inch coming off. Doesn't sound like a lot, but it could take a while to sand it off

The belt sander was faster!
 

I guess I can be fast or accurate, isn't it always the way!

It is only .25 mm
 

I just measured it again and if I can get just .25 mm off each case I can use them.

I may be missing something here but why would you want to shoot 444 brass in your 410? cause you can? just wonding what the thinking is behind your thoughts, that's all.