I ditch all brass used for firelapping. It's a good use for very tired brass.
Yes that Is a good Idea! That brass should not be used again for normal shooting.
I have only fire lapped mil surps , never a S&W revolver....I think I would be scared!
I inherited a number of tins of old Clover compounds from My wife's Dad! Some were never opened!
He was a firm believer in lapping Auto Vales himself in the 1960's.
Also Back about 10 years a go I did a photoshoot for Saint Gobain. They make industrial diamond powders. They gave me about 4 oz samples of all their grits.
I only had to do micrographs through a microscope so I only needed a pinch of each! They told me just to trash the bottles because they could not restocked because the seals were broken!
Well they were trashed....... right to my workshop!
!
Once you get to their 1000 grit series they are dangerous to your lungs and eyes so I needed to wear protection handling them.
(Their "ultra fine" series: I was told, can be put into solution and will not completely precipitate for 2 years)
I have used some of these grits to make lapping bullets for my 98 Saurer und Sohn Mauser