From reviews and youtube video there's folks using this on 50 BMG without loss of zero (
‪Replica ACOG vs .50BMG‬‏ - YouTube)
Now if you're not running a GBBR, consider the cheaper alternatives. The best way to ID the optic is the same are noted by the ARMS mount, lack of trademark, backup ironsight/ doctOr sight and authentic TA01 reticle
http://dragonredairsoft.com/catalog/...products_id=39
http://www.ebairsoft.com/4x32-ta01nsn-base-p-1766.html
http://airsoftdepot.ca/catalog/produ...roducts_id=223