I shot a 3x10 round groups at 13 yards today with my 880.I found that all three groups were pretty tight horizontally (~.5in across) but then spread out vertically (~2-3inches).What does this suggest to you? What might I do to improve my vertical accuracy?I was shooting Crosman 7.9g hollowpoint pellets @ 10 pumps.
Barrel tape mod will help tighten things up the most. Then anything that would reduce trigger pull weight would be next. The "credit card mod" has been brought up a few times, never tried myself. Then ensure velocity is consistent, if no chrony available make sure pumps are full and consistent. A couple drops of 30wt ND oil every so often, maybe every few hundred shots or so on the oil sponge will help keep velocity up and consistent. There are many little tweaks that can be done to the 880 to make them better. But proper oiling will keep them alive a long time. Hope you enjoy yours as much as I have mine. 11+ years and still going strong.
Try jsb exact pellets.