[I bought a Bsa on sale last month and it is worthless.
I zeroed a 7/08 and when I shot it it was about 10 ft high at 25 yds.
I don't know if you can calibrate the thing or not.I tried it on a couple guns that were allready zeroed and it wasn't even close.
Best way for a bolt action is to put it in a vice and a dot on the wall,center the dot looking down the barrel,and set scope cross hairs according.It will be close at 25 yds.aim at the target dot when you fire it,if you can see the bullet hole get a friend to move the cross hairs to the bullet hole while you hold it on the target dot you shot at before.

http://www.hunting-pictures.com/memb...ght&encore.jpg