Bristoe,
The tentative conclusion I came to with buckshot in "modern" rifles is the rifling twist is too much for fine accuracy, especially since buckshot tends to be not quite as uniform a round bullets. Generally I've used a big enough size to be able to swage them down just enough to get firm contact with the rifling.
One of the semi-successes was with Hornady swaged 00 buck in a Beretta Tomcat .32 ACP. Was trying to work up a cheap practice load, and 3.0 grains of Unique matched the velocity of the Speer factory load, and shot a little better. But it sure wasn't a "long range" load!
