II have both a Double barrel shotgun and a fowler. I only shoot shot out of the DB. In the fowler, I can shoot both round ball and shot loads. Many people don't adjust to fowlers because they are, or should be flintlock actioned guns. Shooters who are only experienced with shooting percussion locks are just not prepared for the extra work it takes to shoot a flintlock well. Its a different system, even though you will use the same powder, ball and shot in both guns.
My fowler was made with a relatively short barrel when compared to most of the surviving originals. I have a 30 inch, half round, half Octagon barrel, in 20 gauge. Its shoots .600 RB fine, and it shoots 3/4 and 7/8 oz loads of shot fine, too.
Read the V.M. Starr article on Bob Spenser's Black Powder Notebook site,
[url]
http://members.aye.net/~bspen/starr.html[/url]
As well as Bob's own article on loading the shotgun for ideas on how to load and shoot both types of guns. I think it is very difficult to find a Double Barreled shotgun that will put either barrel shooting a round ball on the POA, using the center bead on the gun. YOu can do several things to a shotgun to move the POI around on that target at a given distance, and this can also be done on a double barrel gun. However, most of the round barrels you find on replica shotguns were just not intended to be used with Round Ball loads. Most shooters want to load up their RB guns with the most velocity they can get. That produces very high pressures, which is not a nice thing to do to treat those barrels. Shooters need to realize that the very large ball that is traveling down range does not have to go fast to kill well past 100 yds, but because it loses velocity so quickly, shots are better kept under 50 yds. Don't load them over the speed of sound at the muzzle and you don't have to deal with the problems that occur when the ball comes back down through the sound barrier( 1100 fps ). At the short ranges that deer are shot, you don't need all that velocity to send that ball completely through a deer.
BTW, the most common reason that shooters have trouble finding an accurate load in a smoothbore gun is because they use too much powder, trying to replicate modern shutgun slug velocities. To even get close requires a very strong barrel, heavy gun, and someone who can stand tremendous recoil. The barrel had better be glass bedded in the stock or the stock can crack, too, just before your shoulder dislocates. :surrender: