I have many reproduction and original smoothbores that I use with shot. This year I shot great with one in Wyoming and other places, did pretty good on ducks with another. With a gun that fits me very well I have done mediocre. While the gauge sizes are different on some, the load is the same. I wondered about patterns and then choke. I got down in the barrel and measured the bore diameter down by the breach and then the constrictions near the muzzle. What I found out was interesting. A 13-bore marked Cyl/Mod is actually TIght IC adn IM as far as constriction. The patterns are consistent with the measurements. The 12-bore that I used for ducks has screw-in choke tubes. Sure enough, the IC and IM tubes are in there and they measure the same constriction as the 13. No wonder I was about equally effective with either using the same load. Another 19-gauge that I have been real effective with was not marked at all, but showed Cylinder and Tight IC for choking. Lastly, the one that had me wondering the most was a 24-gauge. It fits me the best but I am less effective and when I hit something, I tend to get few pellets on the target, even with a 7/8 oz load that is the same as I use in all the other guns. Well the 24 has a true cylinder and the left barrel is just .002 tighter making it essentially a loose skeet at most. When patterning, I had nice, full and round patterns at 15-20 yards and then they started to fall apart. For the few more wild bird hunts this year I am going to stick to the 13-gauge, as the chokes and patterns are effective to a full 35-yards and it's one of the lightest guns I have. For "club" birds that are left-over from other "hunts" when they were released, any of these should do. Basically, I reminded myself of the importance of patterning and load development. You have to know the effective range of the pattern so you can calculate if you're shooting is on par and if the game is in effective range.
