I guess I took it for obvious that I was referring to a Personal Armor (Human Carapace Armor it is called here, and yeah, it is worn by Marsec and Osiron security) not Provost's armor, since it is the former which has 30 armor. Maybe this is not as obvious as I thought.
Sorry for being unclear, I have a tendency to digress a lot. Perhaps I was a bit confused by your approach. If it was me in your place, I'd throw a couple of flasks at their back, then proceed with stun weapons, after hopefully reducing their armor to around 40-ish. Stunning with a RR is insanely risky, especially considering the prize - probably worth losing half of the squad over, even if the boons of such a capture won't be immediately available. But everyone has their own ways of doing things, and that was what I designed this mod for.
As for the Autogun, I think Arthanor summed it up the best. All your firearms suck against hi-tech enemies. You need hi-tech weapons - or specialized weapons - to deal with them. Low-tech weapons, like the ones you have now, will either be lacking in power, or really cumbersome to use (Recoilless Rifle, Panzerfaust), or possessing other tactical shortcomings (melee, flamethrowers).
Autogun is exactly the opposite - with 28/32 power, it guarantees far better hit and kill ratio against low-tech enemies (even Spartans, except for their Terror units you've seen in Hideout Defense) than all aforementioned weapons, due to up to 12 shots per turn, as opposed to 1 shot per turn (at best). Why autogun and not something else of the same class? That's up to everyone's preferences. Yeah lasgun is better, while being dangerous to armored enemies too, but do you have any?
Also most of the lo-tech guns are getting boosts gradually, with upgraded versions and specialty ammo.