Seems my scope target picture changes after a few shots. Not unfocused or mirage or fuzzy, just like a washed out photo. 3 Nikons & a Bushnell, all the same. I try to shoot early morning when it is cooler (?). Mounts on the ARs are one piece steel, 30/30 is 2 piece steel/Marlin 336. Usually 30-60 sec. between shots. AR hand guards are solid tube free float. Wondering if it is the Al. scope tube in steel mount installed in AC cool temp, then going out in the heat. Shooting line has a roof so no direct sunlite Targets are glossy paper but I've used the plain red targets and they do the same. When the color washes out, it's harder to see the POA. Changing focus doesn't solve it. Anybody else notice this?