We leave the locking area on our bolts square. That way if the barrel is really worn it can still be made usable, extending it's life. Parts are $30.00+$8.90 priority shipping. Made by; Precision Replacement Parts Inc. PO Box 2088 Litchfield Park, AZ. 85340 We also have the fitting fixture for this block. $86.00 We can also combine shipping.