I have an FAC mvt in .22 never had a problem I fire air arms field pellets have never cleaned the barrel never had to its always accurate to 5 pence at 60 yards and if I dial in 920fps it will fire at that constantly or 500 fps it will do that the one thing I do is charge it once a month in 4 years of owning I have never had a problem and must have put 30.000 pellets through it .. Does not help you but mine I would not swop or sell