As I understand it, your issue with "1 round per clip" weapons like the Claymoar is that you get killed too often during reload. Since your still getting the hang of hiding the reload animation, which is the use of a power(not all) somewhere during the time between your last shot and the moment you can shoot again (timing differs from weapon to weapon), I won't talk further about it.
Anyway, what it means, is bad management of your offenseless state, be it unaware or unknowing. The a and o, if you think you can't take it, is beeing close enough to cover, so that you can just strife behind it, that won't cancel your reloading like taking hard cover. Or you could use hard or soft cover to begin with, though keep in mind that you should move your left stick a little away from cover, if you reload cancel with the omni button (on console), when using soft cover or beeing close enough to cover in general. Then there's also the use of powers for reload cancelling, just in case you didn't know that already. And at last, just pop an ammo pack! Instant full clip and 100% (iirc) damage bonus for I don't remember how short anymore. You can have a maximum of 6 and 9 with Assault Loadout V. And of course you could also pop an oops pack before or after, whichever the situation calls for.
The rest has been thoroughly explained, I guess.
I see people still can't offhost stuff like GPS, huh? I'd assume, that by now you can predict the AI movements and adjust your aim to the lag. (This is a rant more or less, not directed at you, OP.

)