HXP 303 Now Available

[Son]

I can see how the "O" ring effectively eliminates the headspace buy thrusting the cartridge firmly against the bolt face but how does that centre it as well?
If it's given there is headspace to start with, and it's also given that the diameter of the tapering chamber is larger than the tapering cartridge diameter, then I guess it means that by thrusting the cartridge against the bolt face and away from the chamber this would maximise the airspace around the cartridge.
If the cartridge is truly centred, (assuming the bolt face is perfectly square to the chamber) there would be a perfectly equal air gap around the cartridge and no contact at all with the chamber wall.
I would imagine that you need to remove the extractor for these first firings as I would think that it would push the cartridge away from itself.
The big question....
Where or how does the cartridge reference itself to the centre of the chamber ???
How is this achieved by the "O"ring??
Danny

Danny, I just knocked up a rough sketch in paint to show how the o ring will centre the base of the case in the back of the chamber.
The rubber o ring is uniform is section all the way around and flexible. It will be squeezed into the space evenly all the way around by the bolt being closed onto the case. This should centre the rear of the cartridge regardless of if the boltface is square to the chamber or not.
I think the o ring would be firm enough though to negate most of the effect of the extractor bearing on the right side. In fact, if you watch the extractor closely as you cam the bolt shut, you may see the extractor being pushed outward by the case being centred- either that or it's seating onto the machined slot on the barrel- taking the weight off the case.