You can bring spare 5+, 30 round loaded mags, at least in Oregon, just don't have them in the rifle until you need to use them. I got this straight from a State Police officer that does the illegal hunting decoy stings, but YMMV and I accept no responsibility if you have troubles.
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ODFW Hunting Big Game
Long story short, ODFW can regulate the gun you are hunting with. But that is it, your allowed to carry any other firearm/ammo/etc, etc. that you would otherwise legally be allowed to carry.