I have shot the Noble Sports for years. Never had a problem with the steel rimmed ammo in any of my Perazzis including my SCO. Suggest you Affermann and Ljutic etc shooters send you great guns back to their maker and have their tight chambers fixed so you too can shoot these great shells.
We have shot hundreds of flats of NobelSports the last two seasons on our SCTP team.
Several issues we had were with certain BT-99's that the extractor peeled the brass right off the hull. I don't know of issues with any other guns. I would say they are fine for AIM or SCTP team, or 16 yard shooting.
Their 1265fps handicap loads are excellent for games and Annies.
My son shot probably a fifteen flats of their International 24 gram shells this summer without a misfire. He had two AA's that didn't!
Ammunitiontogo.com and Gamaliel.com sell these shells. If you can get a group buy going, I think a bulk order (e..g pallet) should give you a pretty decent price, per flat. If anyone in the Washington DC metro area buys these shells in bulk, send me a PM. I would be interested in a group buy (I would be good for 10 flats if the price is right).