At the risk of bringing up something that might be better left alone.... there isn't a weight specified for testing in the law.... Yes, I know that an airgun is non-PAL if it's under 4.2 FPE even if it's over 500 fps.... but if you want to take that literally, the intent of adding that rule (so that the police can't use lightweight pellets) really only applies to .177 cal, where pellets are available that are lighter than 7.6 gr. (the weight at which 499 fps equals 4.2 FPE).... I'm not counting things like felt cleaning pellets.... The lightest lead pellet in .22 cal is the RWS Hobby, at 11.9 gr.... Non-lead is another matter, Gamo Raptors are only 9.8 gr., H&N FTT Greens are 9.56 gr., and Crosman SSPs are only 9.5 gr.... They are all commercially available, and you can bet if "they" tried them in almost any "decent" non-PAL gun they would exceed 500 fps AND be over 4.2 FPE....

If you're dealing with a dead stock XXX brand airgun then "they" are supposed to believe the manufacturer's claim, which can even be made with a specific pellet.... IIRC, some Dianas were measured with 10.3 gr pellets in .177 and rated non-PAL, and it was specified on the box the pellets used.... I'm guessing that if you have done ANY performance mods to a non-PAL airgun, and you run into someone whose purpose is to spoil your whole day, with any pellet over 7.6 gr., you better be under 500 fps....

Bob