Years ago( early 80's) I shot on an indoor, not sure how long, min 100 meters, here in WI. It was a test faculty for a ammo produced for Govt. contracts, it is under ground except for the entrance/stat/ section. We shot there in the dead of winter with a toasty temp of 0 deg.(It was less than that outside) Couple torpedo propane heaters to take the chill off. The mirage was incredible. It was located on the edge of Vernon Marsh or at least close by. I can not remember the ammo Company name. They had a production faculty in Baraboo WI. It is possible that the range still exists and it might have been a Gov. installation. It might have been located on or next to a Nike site (remember those) as we had quite a few of those installations ringing Southeastern WI metro area back in the day.