Ruger will tell you that the #1 is a "Sporting" arm and not a target rifle. 2" is certainly minute of deer out to any range prudent to shoot. That said The two biggest issues with accuracy in MOST #1s is barrel harmonics and forearm tip pressure.
40 rounds is not much when it comes to finding the specific load, bullet, velocity YOUR #1 prefers.
Take the best load to date and try shooting off the bench on a sand bag with the forearm removed. Support the rifle on the bottom of the action. If the groups improve or if they get worse it's probably a tip pressure issue. Re-attach ther fore arm without much pressure. The increase 1/2 a turn and see if there is a point at which it seems to "settle" I actually use an inch/pound torque wrench and keep the adjustment in the log for each #1.
Another cheap, quick and easy thing to try is simply insert a small piece of truck inner tube at the front of the barrel channel, Again try different adjustments. This often helps. If it does I usually sand out the factory pressure pad at the tip and simply go with the rubber, It's unobtrusive and practically invisible when done correctly.
We hold an annual Postal Shoot over on the #1 Group on Yahoo. To be honest few guys with unaltered #1s in big game cartridges shoot much/any better right out of the box.
I certainly haven't seen anything to make me think "newer" #1s shoot better than any others, In fact if looking for a "shooter", look for something with a serial number below 130-05xxxx. That will get you a Douglas barrel and a 3 screw adjustable trigger.
Some "general" rules. Most #1s shoot better with a bit of forearm pressure. You'll never shoot one enough that differential heating will effect accuracy by the barrel heating differently than the rib. No reason to cut the rib in half. It MAY help if the rib is actually bearing tight against the front of the receiver to take it off and releave it just a bit and then re-install. Most smiths don't actually work on enough #1s to know what they are talking about/
There is a list of recommended smiths in the files section of he #1 Group.
Were the rifle mine I would simply continue looking for the LOAD your #1 likes best. The dual marked 280s do have some collector value above a "B" with just the 280 stamp but only to the the right guy. I'd just enjoy it. I have a 280 "B" and will admit I don't shoot it a lot any more, however in the past it certainly worked well on antelope, deer and elk.
FWIW there is also several lengthy articles and opinions in the files section of the #1 Group about accurizing #1s.
The best
Ross