My .22 Marauder rifle shoots the H&N Baracuda Match 21.14 grain 5.53 diameter pellets the best ( stock Crosman barrel ). You may want to give them a try. The JSB 15.89 pellets are right behind them.
FYI- Be aware that if you shoot pellets over 900 fps, it may cause lead to build up inside the barrel, which can deter accuracy.
To try and pinpoint what is causing the inaccuracies with your rifle, you may want to try shooting 3- shots groups, with different pellets. This can help to rule out if the rifle has a "bad tune", scope issues, pellet clipping, loose screws, etc.. If you can acheive acceptable 3- shot groups, then you may want to invest in a chronograph ( if you don't already have access to one ) and try tuning the rifle for a low difference in shot to shot velocities, throughout the entire fill - or shot string ( if needed - you can get help with tuning the rife here at the forum ). If you cannot achieve acceptable 3- shot groups, then I would suggest that you call Crosman ( 1-800-724-7486 ) and see what you can work out with them.
Concerning aftermarket barrels; They may be right for you, just know that along with the higher cost; they may or may not shoot your favorite pellet well, and may also need to be cleaned more often in order to maintain their accuracy.
Once you have decided whether to keep the rifle or send it back to Crosman, do your research so you can decide if the groups and pellets your rifle ultimately is shooting is acceptable enough to suit your shooting style, or if it is bad enough to justify the expense and/or maintenance of a non factory barrel.
