Probably a short wad. BPI sells those. I don’t know what they do to pressures with a shorter crush segment. I see that the Gamebore uses Cheddite hulls, so the SG16 or its shorter equivalent would work.
Talked to the Browning historian today about this gun. He said they don’t have any information since it doesn’t have Browning Arms Company on it.
Digging up an old thread but this gun will finally be going to Art next week. Still unsure what to do with the wood though