This was a new one for me today. I recently mounted a scope for a buddy on his M77 7mag. Burris Full Field E1 3-9/40, 30mm. Got out to the range this morning. Buddy takes a couple shots that land about 3 inches apart at 50 yards. He has me shoot one that lands between his two shots, about 3 inches low of the bull. While I was shooting I noticed some blurriness in the center of the scope, chalked it up to high humidity and maybe I breathed on the glass. Buddy fires the next round after a height adjustment and it finds the bull. Here's where things go south. His first shot at 100 misses the paper, second is 4 inches right of the bull. Buddy asks me to try, says the recoil is bothering him and he thinks he might be flinching. I get behind the gun and can barely make out the target backer. Focus adjustment doesn't help. Turning the scope down to 4 power brings back a sharp picture. At this point I know something is wrong but I take the shot. Now the scope is a blurred mess no matter what you do with it, and something is rattling internally. Never had a scope fail immediately like this.

So here is the strange part. Buddy takes the rifle home and leans it in the corner. Picks it up an hour later and no more rattle and clear as a bell. I haven't been able to examine it myself, just going on what he told me. Not sure if he tried moving the dials, focus, or magnification. I don't know much about the internals of scopes. Is it possible a lens came loose and somehow got jostled back into place. Obviously he will be returning the scope regardless but I am curious as to what might be going on here. Anybody with better knowledge of internals have an idea?