The flats should be marked with 2 stars over PSF, meaning High Performance Proof for a Service Pressure of 1050 BAR = 15,229 PSI, and Mean Proof Pressure of 1320 BAR = 19,145 PSI.
SAAMI max. for 2 3/4" 12g is 11,500 psi.

As Bruce said, the B&P MB Classic 1 1/8 oz. at 1330 was a great pheasant load, but B&P has changed their offerings
https://baschieri-pellagriusa.com/hunting/upland-game.html

I do think 1 1/4 oz at 1400 fps is pushing it regarding recoil and the wood.

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