I’ve written about a Manton 9/10 gauge SXS muzzle loader I had several times now. Even though it was proofed 9/10 gauges, by the time I got it honing over the years had turned it into a 8.5/9 gauge. Because of the metal lose due to honing, I decided to shoot 12 gauge loads in it consisting of 3 drams BP and 1-1/8 ounces of shot. It was just fine with that light load (attached is a photo of the gun with a dead hen pheasant as proof). However, I feared what might happen in the field if I accidentally double loaded a barrel with 6 drams BP (which I did once by accident in a Pedersoli replica 12 gauge). I did a 6 dram and 1-1/8 ounce “America Proof” on each barrel and the gun held together just fine. I wouldn’t hesitate to “proof” it if I were you. However, it sounds to me like you have a shooter there.
Steve
