Hmm too bad its not listed on battlelog.
For the past few days i was trying to focus on unlocking the assault class but i found it to be terrible chore. Engie is much more effective especially when you have to deal with enemy vehicles (but thats obvious ). My point is i can not force myself to play assault for the unlocks because my team is not doing its job properly (i have to hide from the tanks and aircrafts all the time). If there are decent enemy pilots in enemy team i always seem to be the only equipping sa-18 igla. I rarely see other engies strategicly placing mines or trying to get better positioning against tanks (they just go "in your face stupid tank" and usually die or basicly do not change position after shot).
Most of the classes are pretty poor initially, but once you've managed to get a few kills / flag captures etc. it starts becoming much easier (hence a tendancy to concentrate more on one or two classes than others - I favour Support and Recon quite heavily), although I have levelled Engineering enough to get the SCAR-H and the AT Mine and Assault enough to get the M416. You can also level up Assault quite quickly with liberal use of health packs (just throw one at any group of people on your team and you'll usually get at least 10-20 points).
The best way to unlock the extra M320 rounds is to have a few goes at Metro on Conquest Large. There is such a tight bottleneck that you can usually get a couple of kills with each round you fire.