Hi Christopher and welcome. Usually, 1300 fps shells but there is a method to greatly reduce the break in time and with using low brass shells. Just store the bullpup with the bolt locked back which will season the return spring for better cycling of even low brass, low velocity loads. Cheers, stay safe and enjoy!

Good afternoon to you. I shoot 00 buck over 1300fps. Hope this helps. Have a good day.
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Usually recommended shells for breaking in are 1,200-1,300 FPS rounds.

Hi Christopher, moist of these Turkish made shotguns require high velocity shells, at least 1300 fps, to break in.
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Stay safe & have a great day!