On almost any conventionally built rifle with a wood stock, you should bed the receiver and float the barrel to realize the best potential accuracy. With a synthetic stock, you can bed the whole barrel.
The next step involves handloading, which you really have to do if you want a tackdriver. It's called the "ladder method" - you load 3 shells at each load, starting 5% to 10% below maximum, then increase the powder in each step by .2 grains (for an approximate 50 grain charge - larger steps for a cannon, smaller steps for something like a .223 or .30-30). You fire these loads, noting the group spread and position (don't worry about zero - you just want to be on the paper). As you approach a certain load level, you'll find that over a .4 or .6 grain spread, you'll have a smaller group, and the point of impact will stay nearly the same. Keep your powder charge at about the center of this range, and you've got your best handload.
