From the posted reg...its very simple
It is illegal while hunting in Vermont to use, carry, or have
in your possession ....
Seems that if someone were inclined to push the point, an interpretation could be made that since the rifle could potentially have a 30-round (or more) capacity magazine, it is an illegal weapon.
Potential doesn't matter, only what you actually "use, carry, or posess" while hunting...
Got only 5 rnd mags on you while hunting? Fine. What the rifle is capable of accepting is irrelevant, so long as you do not do it while hunting.
Hunt with the 5 rnd mags, leave the 20 & 30 rnd sticks at home, you're good (as I read the law).
Have a 30 rnd in your pocket while hunting? THere, I think you would be in violation, even though its not in the gun, because you are possessing it while hunting.
The way the law is stated, tis not what the rifle can do, it's what you do (and possess) while hunting...
Just my opinion, and worth what you paid for it.
Also might want to see if .223 is allowed for deer. Otherwise, tis woodchuck & varmint, and no carry in the woods during deer season. If you have a deer legal caliber AR, go with the 5rnd mags, and leave the rest at home.