Lapping a barrel

[BelchFire]

I have a rifle that's not as accurate as I would want to hunt with. I know it just needs to be shot, but I typically shoot sabots in the fast twist, and I don't think a plastic sabot would break a rifle in as fast as linen would.

I'm thinking about lapping it to bring the group size down. What's the proper procedure?

[FTTPOW]

Belch, there're are a couple ways to do this. The best way is to shoot it, like you said. The quickest and easiest way would be fire-lapping using a snug-fitting roundball and patch combination using valve grinding compound on the patch. The surest way is to make a slug and run it through the bore.
To make a slug you'll need to remove the barrel from the stock and take out the breech plug. Next take a cotton ball and insert it about 2 1/2" down the bore at the muzzle. In one continuous pour, fill the bore with enough molten lead to make a slug about 2" long. After cooling, mark with land on the slug so that you can realign it with the same land at the breech, push the cotton ball and slug out, using a rod from the breech end. Take the slug and from the breech end drill a small hole length wise 1/2 the length of the slug. Take a dowel rod long enough to travel the length of the barrel and still enough left to be able to grab the end with both hands and fix a wood screw into one end of the rod. Use a long enough screw to be able to run it into the slug to the end of the hole you drilled into it. Run the screw in far enough to get a good grip on the slug.
From the breech end take your rod and your now attached slug (coated with valve grinding compound) and run it into the bore, traveling the entire length of the barrel. IF you need to expand the slug, you can tighten the wood screw into the slug to increase the slug's diameter.
A WORD OF CAUTION. Whether or not you choose to fire-lap or use a slug, you can over do it to the point that you can oversize the bore. Use either method sparingly. After a few strokes or shots, reassemble, clean the bore and try a few shots with your normal load to check accuracy. You can always repeat the procedure, but you can't put metal back on! Worst case is that you'll need to increase the ball size and put years of wear on the bore needlessly.