Oh, I'm not 100% sure, well, 0% sure on how government will respond if lets say a bb pistol will be modified to meet firearm criteria. I have no idea how they will even classify it, restricted, non restricted. Technically supposed to be restricted but who knows. Never seen one like that.
P.S Even if you convert them into firearms they might end up on a prohib list of firearms. Idiots compiled a list of about 1500 different models in May. Bunch of us ended up with prohib paperweights
