I did ask Arrieta if I could shoot steel loads through a 12-ga. Arrieta, which was built in 1996 and not stamped with the fleur-di-lis proofed for steel mark. They responded steel loads would be OK providing the chokes were Modified or looser.
I know of a .002 ring bulge at the choke area on the left barrel of a M/F choked 12-ga. Arrieta with 3" chambers. The ring bulge occurred from shooting 3", 1 3/8 oz., #4 bismuth travelling at ~ 1300+ fps. The owner researched why the ring bulge occurred while shooting bismuth and found out it was caused by a phenomenon termed momentum -- too much of a load at too high a velocity through too tight of a hole.
