Not entirely useless... almost - NcStar 50 Bmg Cartridge Red Laser Bore Sighter

Well, when they say you get what you pay for... better believe it in this case. First, the batteries provided were dead and slightly corroded. Second, and most importantly the beam is not focused enough for the purpose of bore sighting a .50BMG rifle. The blob (can't call that a dot) looks like a 1/2" bean at 38ft. Forget 100-yard, or even 25-yard, sighting. Third, the beam is not concentric to the case, thus the bore, making bore sighting a guess at best. The point of aim changes as you rotate the bore sighter in the chamber. In summary if you want to sight in your .50BMG rifle to 10 yards, this could work, passed that.... not so much. As a positive note, it works wonderfully as a tactical cat toy.