Many Thanks DoubleD. I will check out the martini forum. I haven't taken the time to slug the bore yet, but have a supply of .50 round balls to tap down the bore. I do believe the bore is Henry rifled. My group of four rounds was just at 2 1/2". This was the first and only opportunity I have had to shoot the rifle. I suspect that once I get used to the trigger, sights, hold, etc. It would be tighter. With this light rifle, those Ten-X loads of 777 powder (per their claim) really let you know it when your pulled the trigger. I was much like shooting a .500 BPE double I had opportunity to shoot a while back.

Again, thanks. I will try to follow up on my finding.