Hillside Shooting Sports has a rifle range that allows an AR50. They actually rent one. Their rifle range is out to 1000 yrds. also. It is a little far south of South Bend, but might be worth the trip to shoot some real distance. They are located in Roanoke just outside of Ft. Wayne. Roush does not allow 50 cal rifles.
Bottom of the link posted says no 50 cal's. But does look like a nice 1000 yd. range.Hillside has an excellent range and from everyone I've talked to it's a very friendly place to shoot.
If you don't want to drive that far you can check out Youngs. Youngs Long Shot Range
I've not heard of anyone personally going there though. I think its a bit closer for you though.
Bottom of the link posted says no 50 cal's. But does look like a nice 1000 yd. range.
Might call Youngs Long Shot range for more information. It actually says no .50 Cal BMG's. Not sure if that is just full auto 50's or all 50's
Kingsbury is only a 100yd range
The range in Winamac, according to my understanding, does allow 50 caliber rifles to be fired. I went there one day and I saw a Baret 50 cal