I've always considered the BM450 to be a hunting rifle, not a tactical one, since the power and recoil is more than you will need or want for close quarters. For that reason, I would not go for a tactical scope, like a 1x red dot, reflex or holographic. Since the range is limited (300 yards, in my opinion, to be sure of a kill shot on a large target like an elk), I would go with something suitable for deer hunting, like a 3-9x. I am using a Leupold VX-R 3-9x40 with the Ballistic Firedot Reticle. Here is a reference - http://www.outdoorgearbarn.com/p-17843-leupold-vx-r-3-9x40-illuminated-firedot-duplex-reticle-matte.aspx
. If you are going after hogs, then in that case I might want something in the 1-4x range, if distance shooting beyond 100 yds is not a consideration. There are also some less expensive scopes that have been reported to have held up well, like Burris. Optics Planet is a good source - http://www.opticsplanet.com/riflescopes.html
, and for the bargain basement, I like Sportsman's Guide - http://www.sportsmansguide.com/productlist?k=scopes
Another consideration is rings. The Burris PEPR mount or similar ones from Nikon and others seem to be popular.