vigillinus,
I bet they would have been a nice pair of rifles.

Do you have any thoughts on why the .318 extracted and ejected well while the .375 was not as reliable?
I guess both rifles would have had similar quality and fitting of the extractor parts so do you feel that maybe one cartridge case type worked better than the other?
Depth of the rimless extractor groove in the cases could have been slightly different maybe?
It's interesting to hear that two rifles from the same maker could give different results.
This is something that has cropped up a lot over the years, where some doubles seem to work reliabley with rimless cases and others don't.
I see that some Holland Royals used a broad land type extractor on their rimless doubles and this seems to give a greater contact area between extractor and case.
I have never handled a Westley chambered for a rimless cartridge so I have not had the chance to examine how the extractors are made.
Do they use a single spring loaded type pawl similar to many modern doubles?