I recently bought a Bushmaster BAR-10 and Id like to get some back up sights for it. I was wondering if these sights are calibrated only for .223 or can they be used for .308 too? Thanks for anything you guys can pass along.

Many (even most) BU rear sights are not adjustable for range. They are what their name suggests, a BACKUP for use in the event that your main optical sight fails. Just pick one you like (I happen to use a DPMS Mangonel) and zero it for your chosen range.

If you plan on shooting with irons a lot and want to be able to adjust for range, you can either (1) ask Bushy/Armalite if they offer an AR10-specific carry handle, or (2) get a National Match rear sight and zero by number of clicks.

ok cool thanks bro