It's funny, I have found that Remington brass doesn't shoot nearly as good as Winchester in all my rifles. It seems a lot harder and decent for hotter loads, yet more inconsistent than some other brands.
Still different rifles like different things, and brass can be one of those things thats for sure.
Was the new Winchester brass neck sized only or FL sized?
Did you take calipers to them to see if they were consistent in length?
Sometimes they can be off just a hair and that will effect accuracy too. After fire forming, Winchester brass works great for me.. to each his own I suppose

You got a pretty good hunting load there, always a good fall back.
-Aaron