Just because you have good chronograph numbers doesn't mean nothing if your gun is not accurate. My rifle has a 500mm barrel . My best numbers with hybrid 22 grain slugs was at 974 fps and spread of 10 fps. 2.9 std. Best group was .685 at 50 yards. Definitely pushing them to fast. Tuned down to 950 and groups are getting better. My number with the monster jsb was best at 935 but not shooting good dropped down to a tune with a worse std and spread and average of 912 fps and shot three groups that are very good for me. Two of them are the best groups at 50 yards with pellets that I have ever shot...you never know!!! Bottom groups for for panthera.