Is it a time tested Bore/groove combo for pellets or a compromise to make everybody happy or try too. While watching football I decided to to measure some pellets.. The JSB 18.13 ran .21795 mostly & the skirts at the smallest .225, very hard to measure the dang skirt..So my question is why more are not running RF barrels.? Not enough bite between .217 bore & .218 pellet ? the skirt certainly seems ok for .217 .222 RF barrel. There is also .22 RF tite spec stuff, more like .215 x .220. But I can't seem why a normal RF .217x .22 wouldn't work. I get the whole slug spec thing but for pellets I think I need it spelled out for me as to the why of it ..lol I'm missing something I think. The twist rates are close enough. 16 common & many more available.