Got my Stoeger Bullshark .177 last week. It came with a full fill, but i let it sit for a couple of days & no leaks. Everything was tight, & a big improvement over my P15, so I cleaned the bbl from the muzzle with my coated Dewey rod. Got a ton of dirty patches. Finally shot it over the weekend & was sorely disappointed! I could not get any 8.4 pellets to group under an inch at my 20 yd basement range. I adj'ed the hammer spring down to 680 fps, up to 920 & I still got flyers. Figured i lost the SPA barrel lottery? I decided to try the JSB 13.49 pellets & it now puts 5 shots into one hole at 20 yds with a sst at 840 fps. In my case, the mags are the problem. Shooting with the mags, i still get constant fliers but with the sst i made it shoots 1/4 / 5 shot groups. I will be ordering some Carm mags after the holidays for sure.I know not everyone has had mag problems but I've narrowed my problem to them.