I know Lyman and everybody says size your bullets to the groove diameter, but I have found much more cast bullet happiness sizing them to fit the throat or no more than .0005 smaller. That way if the throat is larger than the groove diameter, which is the case in 99% of rifles, you don't get a bunch of blowby between the case mouth and the bore. The way to do that is to either use cerrosafe and make a cast, or make an impact impression of it. Since I learned this trick from Veral Smith I have had way better luck getting cast bullets to shoot in rifles. As for a bullet, try something like #311299 if the bore is right on the money at .300. If it's bigger, you might try #311284 or some other non bore riding design. If really big, sometimes #313299 can be used to good effect. Just have to see what a chamber cast tells you it'll need. And yes, that's sure a good way to get youngsters shooting centerfires! My daughter loves to shoot the 30-30 with 7.0 gr. Clays - it's not loud, super accurate, and no recoil. Plus she gets to help out reloading them for the next outing.