Thanks for your thought fellas. Both round nose & pointed spitzer should feed smoothly. They have done on other M1903 MSch rifles I've had in the past & this should be no exception.
Both types of rounds jam in the same place.

As I can find no other flaw, I'm coming to the conclusion the spring tension in the rotary mag. is not perhaps what it once was. I think this because the cartridge release spring seems normal and the round (Cartridge) seems unable to push over the restraining tab as the bolt face is moved forward.

I shall probably have to strip the spring in the rotary mag & try to either fix or obtain a replacement.
I cannot see any other material factor that may any relevance in lifting the case from the magazine.

The OAL of the cartridges is: 140gn spitzer 3.063" & 159gn RWS factory round nose: 2.974"
Cheers.