I'm new to this, but from my limited experience....with only 2 mags you'd need to have multiple speed loaders full on your person and probably a small spare bag of BBs on you also, to refill the loaders. In a pinch you can maybe get some BBs in a mag under fire, but it's a really difficult move not to fumble things in this situation.
Your best reload opportunities would be if there are short briefings between missons. I do believe your team will count on you to 'get back in the fight' as quickly as possible after a re-spawn. That's how I try to play it.....