So, instead of multi-quoting every post above...
MisterHappy,
Here comes the opinion
1) Echoing crack-pot' sentiment, please don't use the noise of firearms as a means to annoy or seek revenge on your neighbors. In this state the best outcome will be major legal fees and time in court with you LTC revoked during that time.
Now that that's out of the way, time for the next point:
2) In my opinion, without legal fact, IANAL, YMMV, etc.. I have not been able to find a definition of a "test range" in mass law, nor have the fine folks at GOAL when I inquired about the same.
It was recommended to me, that absent a definition, my best bet would be to build such a range to meet or exceed all NRA standards as found here:
http://www.nrahq.org/shootingrange/sourcebook.asp
And then with that, once I'm standing in front of a judge with Atty. Reddington by my side, I might just have a defensible case. (ok, Reddington wasn't specifically recommended to me by GOAL)
So the net is, Massprudence prevails, and you have no right to disturb your neighbor's safe and warmy, even if they destroyed your property.
You do, however have the right and duty to recover the value of said property.
I would file a claim with my homeowner's insurance to cover the vandalism telling them how it happened.
For a moment, I though you were my new neighbors who just moved in, and I was just going to invite you to come shoot at my range.