Hi -

I am new to the board and trying to learn something about late serial number Krag "carbines" I have shot and reloaded for.  The first was a rough, clearly aftermarket W. Stokes Kirk type carbine S/N 478,704 with an 1898 marked receiver, and a light 1901 cartouche on sanded carbine stock.  The second is a much nicer, armory correct looking carbine stock with crisp cartouches, S/N 477,356 with JSA 1901 cartouche, 1898 receiver, and W. Stokes Kirk band front sight.  The interesting thing about both of these carbines is that both chambers size the shoulder of the cases back when fired, leaving a distinct sharp ring where the neck and shoulder come together.  When I resize the brass, this ring remains.  Neither my 1895 Winchester in 30 US nor my 1896 Krag rifle do this to the brass.  The tight chamber also makes closing the bolt difficult, especially on reloaded brass compared to factory loads, probably due to a little work hardening.  When reloaded rounds are fired in the correct chambers, they will fire form back to a full chamber shape somewhat, but the ring is still visible. 

My questions are:

1.  Why do these high serial number/surplus cut down carbines do this?  Did the aftermarket supplier have a bad chamber reamer, or is this found in some late Springfield made pieces as well?
2.  Is there an easy way to fix the chamber without removing and cutting the barrel after re-reaming, which would mess with the sight location in relation to the hand guard?
3.  Is there a safety issue with firing these rifles? 
4.  Is there a source of a new sight blade blank for the W. Stokes Kirk band type front sight?  Mine is too low, I could a new one but if one is out there which would drop in it would be easier.

Many thanks in advance for your thoughts.