Benny, I had a (German) Zeiss lock up and freeze its erector in the heat of the Kalahari once making the scope a fixed power. Luckily, it was on 5X or it could have been a big deal. That rifle (300H&H) now wears a fixed 4X and it is just fine. Depending on what you want to use the rifle for, but if it is for Africa or the like, fixed would get my vote.