Originally Posted by AlexS
Wait a second. I'm a slow thinker from the european mainland.
Do you mean, that grain is a force, equivalent to newton and not a mass that is equivalent to gram?
grain isn't a force, but that's not the problem.
The problem is that Foot Pounds Force (FPE) which is how the UK law defines a legal airgun, is a force that is different depending on the value you use for gravity (which believe it or not, isn't constant)
Joules would be a much better definition in law, but we have a crazy law