Hey jpshaw:
The guncrank1 told you right. Put enough 88 or 33 elec. tape on it, enough to keep it snug, not too tight, if it is a little tight it don't hurt anything. Most of them should have a o-ring for snug fit. I have made serveral since then and all work OK. The first one that I made, I used the 12ga. shell for dimensions and it was pretty loose, I taped it and it is fine. No rifling means poor accuracy almost always. The rifled ones are a little more accurate, all are fun if you don't expect too much in the accuracy dept. lol
HM