That's exactly what I do with dimensional masters or dummys. That hole looks too perfect not to have been drilled so i think a dummy that you picked up made it's way into your brass stash. The displaced brass is also on the inside which further suggests that it was drilled or punched from the outside.

I crush my case necks, seems a complicated thing to do a punch from side ?

I think there was a grain of sand or ?? that got caught between case and chamber. I was teaching a newby to reload this came from a batch of cases he had bought from a non reloader.

I hear your too perfect sentiment, first thing I saw as well, but wrote it of to chance ?

I crush my case necks, seems a complicated thing to do a punch from side ?

I think there was a grain of sand or ?? that got caught between case and chamber. I was teaching a newby to reload this came from a batch of cases he had bought from a non reloader.

The hole I frill in the side is not to deactivate or ruin the case but rather as a clear visual and tactile indicator of the fact that it's not a live round. Commercial training dummies that use brass cases often have them too.

To destroy iffy cases so they cant make it back into rotation I also just crush the neck.

When I say dimensional master, I mean an assembled inert round that has all the correct dimensions for a load I've developed.

The roundness of the hole as well as the burrs on the inside seem to indicate that the hole was drilled.

Definitely not dirt in the chamber.  A piece of dirt, small enough fit to between case and chamber, would only make a small dent and likely be imbedded there.

would only make a small dent and likely be imbedded there.

Yeaaaaa !!!!! u right.

Had a look again, not round hole at all, almost square.

Got it, it was drilled, but the metal kinked away, hence the round from one angle and square rectangle from another. In the original pic the case is at the angle it looks round, at a more 90 degree look on, it is oblong, rectangular. The metal gave way as it was drilled, also why hole is clean onside inside and burred other side inside.

Had me going this hole  ;D  ;D