A question I've had for some time. I've noticed that break-open rifled arms traditionally favored rimmed ctgs. And many contemporary ones still seem to.
The traditional explanation (after rimless rounds became widely available, that is) was that rimless extractors were complex and unreliable. Clearly we have got past that long ago (except in stopping rifles where perfect is the only standard).
Another is that equivalent rimless rounds exert more thrust against the breech face than their rimmed counterparts, say a 7x57 vs. a 7x57R. So the RELATIVELY weak break open actions are stressed and worn less by rimmed cartridges, all other things being equal. Apparently this is because the larger surface (head + rim area) of a rimmed cartridge distributes the thrust force more widely over the breech face than a rimless ctg. which has only the area of the head.
Is there anything to this latter argument? (I understand it takes a degree in mechanical engineering to give a REAL explanation, but is it true as I've stated it?). Even true-ish?
Yours in ignorance, not bliss,
Mike Armstrong
