"Compatible" means with the following proof marks, indicating "Standard Proof" for LEAD OR STEEL limited to no larger than 3.25 mm / U.S. No. 4s and max. fps 1,300. There is no choke restriction for "Standard Proof", but most recommend limited to modified. No. 7 steel target loads MAY be safe with full choke.

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12g 50mm, 60mm, 65mm, and 70mm “Standard Proof” is for a Maximum Average (SERVICE) Pressure 740 BAR = 10,733 psi; Maximum Statistical Individual Pressure 850 BAR = 12,328 psi
Both 65 and 70 mm 16g standard is SERVICE 780 BAR or 11,313 psi; MSIP 900 BAR or 13,053 psi

From the Gamebore site

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Reproved 2012 for "Standard Proof" after honing

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