The two little internal ribs go to support the notion that it is a vibration damper.and a physical means of re-centralising the barrel after it has moved. Although 'moved' is a bit of a misnomer I suppose. Should that read '...finished vibrating'. I have to confess that I didn't realise that the inner band was internally tapered. We only got them assembled to new barrels and the last new Ordnance issue barrels I ever saw were in the 60's.

There were several simple student experiments that could be used to illustrate the vibration characteristics of rifle barrels, especially light ones like the No1. The first one was the fact that you could use one as a post horn (a musical instrument......)

Interesting thread