Gents, I have an old Mossburg 22 that was give to me a bunch of years ago, it was from the 60s and in pretty beat condition.

It was accurate as hell so I decided to restore it as best as I can. I completely refinished the stock and it looks like a million dollars. Removed the barreled action and gave it to a guy to sand blast. He already completed a portion of it and it's a matte silver color now, looks incredible with the new stock. I initially planned on blueing the rifle the way it originally was, but I think now I'd like to keep this look!

Is is possible to just leave the steel as is? or will it just rust too quickly?

Any options for protecting the steel while leaving it's current appearance?

Thanks!

You can keep unfinished steel coated with something to prevent rust, such as Birchwood Casey RIG, or a film of wax (as some waterfowl hunters do).

It's not common today, but older military weapons like the British "Brown Bess" and Imperial German Gewehr 98 had large areas of unfinished steel. It was a measure of a soldier's discipline that they keep their weapon maintained and rust-free.

Of course, it's easier to let a surface finish prevent most of the corrosion. That's what I prefer.

Brown Bess came browned.  That was the traditional finish before blueing.  
Properly browned barrels hold oil in the browning.  It's actually a controlled rusting process.

I don't think they did, at least not prior to the American Revolution, but I'm certainly no musket historian.

http://www.militaryheritage.com/browning.htm

You could always clear coat it and be done with it.

I thought that was patina not a deliberate browning process.  Our civil war muskets and rifles were the same, no finish.

Lots of bolt action military rifles had their bolts polished but not finished.  Ie the Swedish M96, the Swiss K31.    The advantage is I can buy an old gun with a rusty bolt and hit it with crocus cloth and keep it oiled.  In a few years there is an old dry oil patina on the bolt.

Look into clear cerakote or a zinc coating.