Ross .280?

I have a couple Ross 1905's I'm lookin at. The military one is as per issue. But the sporter Ross is unique indeed!
1905 looks like a very well smithed sporter or factory made that could be .280 cal.?
The bolt body and receiver are hot blued almost to mirror finish and the bolt head is polished or plated nickel. Barrel is quite narrow and 24 inches long and nicely blued. The rear sight is polished and is grided in incriments of 20 yards based on a dial that is knurled and goes around entire barrel dia. . Custom light trigger different from issued 1905 but does have Ross proof mark.Crown over 6 over G. In fact the whole trigger mech differs from the as is issued type.The trigger guard is also lighter and this guard swivel is much thiner than regular 1905 issue.It also has a Mag Catch in front of trigger to assist (I think) with another cal. as it ends on top of Magazine platforms left and right sides.. Hot blued too.
Stock has 8ZZ. DarrowC and cross rifles.It is checkered with recoil pad No where is there a calibre or tons pressure stamps. This stock is made for the narrow dimensions of the barreled action as they do mate nice and tight.
I cannot get my .302 running bore guage to even come close to entering at the crown or throat. .303 drill rounds do not function out of the mag. The bolt face even appears different.
I guess I will do a chamber cast,first time in 15 years, to confirm my suspicions.
But I do need help telling me if this is a .280 factory Ross I have heard so much about over the years. I have handled the Deerstalker and this is different.

Early .303" Ross had a bore size of .298-.299".
Swivels on early Rosses were lighter as was the trigger.
Sounds like military proof mark and sight Ross MkII. Catch in trigger guard is mag cutoff.
Early .280s were built on a modified M1905 action(M1907) having seven IIRC locking lugs.

It might be a .280, but could also be an early .303 and maybe rechambered to something else.

A real .280 would be marked over the chamber with ".280 Ross".

If yours isn't marked that way, take it to a smith to figure out what caliber it really is. For all you know, it could be rebarelled to .25/303 or something.

It sounds as if the rifle is a gunsmith made sporter. The factory did make sporters on the 1905 action which incorporated military parts, but that pattern of rear sight on a factory sporter would be most unusual. Does the rifle have the Harris magazine? Apart from the II** rifle, 1905 barrels are slender.
Rebarrelling a 1905 receiver with anything other than a factory barrel would be a real challenge, because of the unique characteristics of the 1905 barrel shank. Of course a 'smith could cut the shank off factory barrel, and install it on a replacement blank.
Any chance that you could post or email photos?

Thanks Tiriaq and others for the info here and Emails.
I slugged the barrel, a very tight .310 (.303). The lands on this barrel is around .298. The bolt face looks incorrect but I will compare it to others next week. Then hopefully I can shoot it.

based on a dial that is knurled and goes around entire barrel dia.

I think from your desciption of the rear sight that it is a H. L. Block sight that Ross used on 1905 rifles before they started to use the Sutherland sight. Any pics?