I dont think the cant the sights to allow for drift, thats what windage adjustments are for. I think its just a screw up some where along the line. I wouldnt put up with it if it was me.
First get it running and see if the barrel shoots worth a hoot. If it does, pull the barrel off, index it so the sights line up, (by shorting the shank and shoulder of the barrel, run a finsh reamer in it to get it head spaced propertly, then shoot it.
If it dont shoot, replace the barrel.
I certainly wouldnt put up with a gun with the sights hanging off the side of a barrel.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071