Why don't you just cut the barrel down to fit in your oven? Seriously, I recently refinished my SKS Paratrooper in my oven utilizing Brownell's Teflon-Moly oven cure finish. I was fortunate that my oven fit the shorter barrel.
I think the secret with these types of finishes, whether you do them yourself, or have the true professionals like Mac's Shootin' Iron Restorations do it, is this: Let it cure as long as you can (like a couple of months if you can).
I've "heard" that you can spray these coatings on, and that in time they'll be as hard as if you baked them. I've also heard of people setting up expediant solar ovens (i.e. throwing a freshly sprayed piece on the dashboard of an old car and letting the sun heat the metal up for about a day) - YMMV! (you may live in Wisconsin)
If you're just pulling your hair out - as a last resort - I'd try using the oven with the door open, and then maybe swapping ends after 25 minutes or so. That may work, but in my opinion it is far more important to make sure that you have a prepared surface that is perfectly clean and devoid of oil. Good luck!
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"A belief is like a guillotine, just as heavy, just as light."
-- F.K.
