I often here that the fit of a pellet, in the breech, needs to be snug. Well, I have this 1992 TX MarkI and the pellets almost fall out of the breech unless a Crosman Premier is used. I think the skirt on the AA/JSB is the only thing keeping the air from just blowing around the pellet. I shot 20 or so out at 55 yards, FT style, and then walked out to refresh some really shot up places on the paper with some 1" orange dots. Using AA Diabolo Fields in 4.51, no it's not a .22, my first 4 shots hit the 1" sticker with the last pushing it through the worn paper backing. I retrieved the dot and all 4 were within a .5" area. This gun must really have a wonderful choke, because the breech is so sloppy. I had tried a JSB 4.52, but they don't group as well. The skirts have a different shape to the hollow area so I think I might try some 4.52 AA. I know common knowledge is that the number means nothing, but the 4.52 JSB definitely fit just a touch tighter. Hoping the AA 4.52 will as well, but I don't see how the accuracy could improve. Did I mention that this gun has a nice little buzz to the firing cycle? Tight guide and loose tophat, but I'll not touch it as long as it's so accurate.