Terry,Are you into blackpowder and have muzzleloading equipment available to you to use? I'm assuming the Chamber size is known? I had my barrels magnafluxed and were deemed sound. My chamber is 2 7/8th inches.
I started loading this year for my 10 have had great success with 4.25 dram loads, 115 gr. and 1 1/8oz of shot. I trap shoot with lead and will load #4 bismuth. This load I'll pass on if you interested, it fits perfectly into the hull.
I had my 10 out at a trap range locally and the look on peoples faces when 115 gr. of blackpowder went off and clay birds were breaking was priceless.
I got all my supplies at Ballistic Products, Federal primed hulls, wads and my roll crimper. You could get your wads from Circle Fly, probably 9 ga wads for those brass hulls. I'm not sure what primer though? There is great information about loading brass hulls on the Circle Fly site too.
Hope this helps.Good luck with the geese. The Illinois waterfowl season starts this Saturday.
Vince