Sounds like a Redfield 102.  Is the front sight banded around the barrel?  I suspect that yours is a cutdown (reduced from the original 30 in. barrel to the carbine length of 22 inches).  Replacement aperatures are available... although Butlersrangers is the resident authority on Redfield sights!

If possible, please post some pictures so we can get a better idea of what you have.

Paul