I play airsoft in NJ, NY, and PA and I was looking into the legality of owning and using blank fire airsoft grenades. These grenades are essentially a striker that activates a blank cartridge or a primer for the purpose of making noise (est. 120+ db). I have seen a ton of conflicting opinion but no facts whatsoever. I would assume the legality would depend on the state you're in (info for NY or PA also appreciated) so I am focusing on NJ which is my home state.
Here are some of the forum posts I have looked through. AMS Forum Post rules exclude them, not based on laws. Reddit Post talks about the ease of converting something into a zip gun. I think that kind of ruling would be opinion based on how hard it it to convert. Airsoft Society Post Minnesota classifies them as fireworks which makes them legal.
One thing I found classifies blanks (at least pistol caliber) are not "handgun ammunition". I don't know if that helps.
I think my next step will be to contact the NJSP Firearms Investigation Unit. I don't know if it will go anywhere but its worth a try.