A picture of primers fired in my 929.

I was quite concerned
I normally don't post my loads. But, these were, a 147 gr. xtreme plated .356 bullet,, with 3.5 grs. of Bullseye,, Federal SP primers, 1.135 OAL averaged 853 fps out of the 929.
I usually used only Winchester brass in the 929,, but tried different brass to see if it made a difference.
Never had any problems with them ,, but it sure flatten the primers in the revolver.
I don't have a picture of the same load shot out of my autos. But the primers were not flatten at all, and average 950 fps out of my autos.
I also have other firearms that uses moonclips and rimless cartridges and have never noticed the primers this flat?