I have a 6 1/2" T/C .45-70 barrel (it was a gift). I tried a 1" Ultra Dot on it, because I have 6 others which have given good service on other guns. However, with this barrel, the battery kept popping loose, and of course the dot wouldn't work. Fix it, and it would work 20-40 rounds then pop loose again. I finally replaced it with a 2X Leupold. That same Ultra Dot works fine on another gun now.