Bruce in OZ: I had noticed that in my spares and you'll often see the wear marks on the barrel from where the barrel rests on these flats. I have one MkIII (1916) made by Enfield from a former MkI that shows wear marks about one inch apart due to the relocation of the inner band in the new model. The little flats certainly seem a good way to positively relocate the barrel after each shot and I've extrapolated this to the front bearing on a couple of No. 4's that were not grouping well. While they had good up-pressure, the barrel channel was of a larger radius than the barrel and didn't positively relocate it after each shot. I scraped a smaller radius groove at the bottom of the channel (inverted analogue of these inner bands) and now the barrel is very positively located. In one case the grouping clearly improved.
Ridolpho