Chris said:
There are also other laws on the books regarding "Infernal Machines" that could be brought up.
Sorry, I actually did mean "infernal machine" charges.
The police may be "reaching" but here are some of the MGLs that they are looking at using to charge people with them.
C. 266 S. 101 - if used to create malicious damage
C. 266 S. 102A - infernal machine
C. 269 S. 12B - minors in possession of an air rifle
Also be aware that some towns have VERY broad definitions of what is a "gun" in local bylaws prohibiting shooting within the town.
Whether charges stick or not, the interaction with police may make one deemed "unsuitable" for LTC, as well as an expensive lesson in how our "criminal justice" system works.
If I had one and was intending to fire it anywhere that was near habitation, I'd probably discuss it with the local chief first to avoid confrontations. Otherwise, I'd only do it way, way out of town in the mountains somewhere that nobody would be calling the police.