Seventy five yards is pretty much it for most smooth bores. My old Model 37 Ithaca Deer Slayer(bought in 1977) is a heavier barrel and the gun smith that put on a scope mount told me that it the barrel is tappered along the whole length of the barrel. The scope made no significant difference. I can keep the best fitting slug (brenneke) within a six inch circle at around 90 yards.
Roger, if you will NEVER ever shoot beyond 75 yards buy it. The deer will drop like a rock. Not much out there likes a .69 inch hole put it it. If you think there is the smallest chance you may shoot at a deer beyond that, look for a rifled barrel.