James, While I have had decent luck with Norma's I have, some guns don't shoot them well.I'd try some from JSB or H&N. While each gun has it's favorite pellet... even those can vary from lot to lot. Another possibility is the scope on a springer. Are you using the bundled scope on your Gammo?Do you have another "Spring Gun" rated scope to try?
I'm fairly familiar with shooting springers and can get some tight groups with no fliers when I do my part correctly.Frustrating for me when I do get fliers because I'm certain most of them are MY FAULT!I typically relax a little too much and forget one of the 12 things I need to do PERFECTLY every shot.Yeah, springers can be a huge PITA but I still love shooting them:-)
Yeah, 4"-6" is extreme. All random or more horizontal or vertical?I do get fliers that were NOT my fault with CPHP 22s in a couple springers. I can "feel" them as really tight or very loose breech fit and can also trace wide shots as a large variation in shot velocity. For me, pellet "fit" variation SEEMS to be more important than weight variation.
I don't think tight pellets and 8 fpe go well together. The gun may have real trouble getting those pellets moving, with resultant variation at the target.