Try the free public range in Glastonbury. They only allow paper targets, but I'm not sure if they limit shotgun loads. At least, give them a call b4 driving over there....
"The range will remain open through November 30, 2008 and will be staffed by seasonal DEP employees that are certified range safety officers.
...Only paper targets will be allowed and shooters should be reminded to bring eye and ear protection, which will be required at all times. Rifles, shotguns, pistols and muzzleloading rifles may be used, however fully automatic weapons are not permitted."
http://www.ct.gov/dEP/cwp/view.asp?A=2711&Q=412550
I actually called today (Monday 27 Oct), but the range staff don't work at the office during the week. The office had no idea as to ammo restrictions etc.