I also have a 20-50x--used it at about 40x on my 6.5-284 to take the doe that i am posting in the LRH section (once i post this)
I use it at full power in 500-1000yd BR matches--i can see holes in white paper easily to at least 500M
havent shot past 1K with it, but I do love my 50X
JB