Airsoft found a solution, maybe
Interestingly this raised its head in airsoft a while ago and worryingly, maybe for airguns, lethality (If I recall correctly it was this term) was set at 1j. This was deemed as the speed of a bb to break skin and draw blood. This was set to be 328fps with a 0.2 gram bb.
Certain sites set this as an absolute limit other allowed up to 500fps but set minimum engagement ranges. If one looks into the regulations to buy an imitation airsoft gun you have to have it coloured brightly unless you can prove you use it to skirmish. Maybe not related but essentially they reached this and it is accepted from a legal standpoint. (Waivers and disclaimers turned out to be pointless as over 1j it became an absolute offence and the cps technically didn't need a witness willing to press charges they (cps) coukd do it anyway. Whether there has ever been a conviction I have no idea as I used to airsoft years ago and haven't for a long time. Maybe the airsoft community could shed some light as it's so easy to raise the power of an airsoft gun.
Random point for muse why isn't paintball suffering the same problems? Or,is it because they are technically paint markers not paintball guns?
Tampering with evidence is a very interesting point but unless there is a standard test laid down and calibration needing to be proven; you can get off a speeding conviction if the radar guns/pursuit traffic cars speedos etc.
Final point is shotguns being limited to three shot without section 1, many are capable of more with off the shelf mag extensions. Has there ever been a prosecution?
All in all I also believe there needs to be a set test that's scientifically laid down but as we all know more worrying issues are ahead with the possible licensing off all air weapons (I use that term advisedly and some may disagree) in Scotland. Hopefully the sheer administrative burden will stop that but only time will tell.
Ps I know some will pick up this is my first post but that's ok with me.