In my email I asked specifically about homemade air rifles, which are fairly common in N.Z. due to bored farmers, and why there was a grey area unlike in the U.K., Poland and Canada where there is an exact number that can tell the difference between a restricted air rifle and a non-restricted air rifle.
I think only my hybrid would technically fall under a firearm, all my pneumatics would still be air rifles but just require a firearms licence. There is a permit required if you want to make firearms but I guess I'd have to ask if that extended to air rifles.The problem is even tough a powerful spudgun is considered like a firearm, it doesn't mean it's legal to use one with a firearm licence, they often have to be declared and often have to go through a whole load of tests to establish that they are safe to use etc...