A friend whom is now deceased owned 10 4 bore guns. I went to his house and measured all from muzzle to breech. He wanted a choke gage made and I made him a 10 to give to friends that has 4 bores. He wanted them made out of brass and I told him he would need a holster to carry one, but he insisted. From those readings for choke we averaged the readings and came up with
cyl/bore .935
imp.cyl. .920
mod. .905
imp. mod. 890
full .875
Some of these were single barrel.
He also had 28 8 gauge guns mostly doubles. He owned the only two consecutive serial numbered Quality 4 L.C. Smiths.
This ought to give you an idea of what you have.
