Insufficient Head Space?

[jmoore]

It occurs to me that the numbered bolt head system that probably worked fairly well with new parts throughout, now merely confuses the issue of proper bolt head replacement. The old SMLE/ No.1 system makes better sense when dealing with used parts- The replacement heads were oversized and were individually fit to each bolt, then fit to the rifle.

It also seems to me that the bearing surface on the face of the bolt is smaller (due to an internal chamfer) on No.4 rifles than on No.1's, so that wear may occur faster.