Well even for a mixmaster Winchester you can still be looking at 600-700, and if you get lucky and some folks get in a bidding war it could go much higher.
I have seen mixmaster Winchesters sell as high as 1000, but that is really unusual to see it go for that much.
I would say the 6-700 is a more likely price but you may get lucky.
Is the Barrel a Winchester? You didn't mention the maker on that, and if it is a Winchester barrel its very likely an original barrel receiver combo; the date is right, as you rifle was made on 3 July 1918
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