Quoted:
Will two belt mounted AR mag holders be sufficient? I don't have a tactical vest or chest rig. I can always pick up a cheap condor chest rig if you think it would it would be beneficial.
I brought a chest rig to my carbine class with the idea that I would refill my two belt pouches. What happened in actuality is that I was the only one who was thinking about this so I ended up ditching it after the first couple reload breaks as we were stopping anyway.
What you really should do though, bring as many loaded mags as you can. I know I got to pick Glen's brain a lot and rehydrate more often because I already had my mags loaded. When it came time to reup the belt, I just grabbed a couple fresh mags out of the bag and in went the empties into another. The other guys were reloading mag by mag and you could tell after the 10th time doing it that they were over loading mags. This also gives you more time to relube, tie your shoes, whatever you have to do, instead of missing drills or feeling rushed.