Interesting photos, both military model Ross rifles! I have several Model 10 sporters in .280 chambering. Great rifles, if with ''note of caution re bolt assembly!
Your reference of inquiry I 'assume'; the rifles' with almost consecutive serial numbers as appear in second from the top AND the reference to barrel attachments as reflected in sixth photo from the top.
Re your question... No idea. Just here, to clarify your apparent relative photos of interest.
Best!
John