I think 2 things are being discussed here. Real cap and ammo cap.
Real Cap - as in an equivalent to it's real world counterpart eg. M4 = 30 rounds; P90 = 50 rounds; M14 = 20 rounds etc...
Ammo Cap - everyone is permitted to load to a maximum capacity per mag.
I see the benefit in both but often do see more games lean more towards ammo caps where everyone's mags are loaded to 30 rounds and no more.
The idea is that it levels the playing field and no one has an advantage over another regardless of what type of weapon you can afford or have working at the time.
With a real cap game, where you're limited to what the real weapon would carry, you can get into arguments about what a particular weapon's maximum capacity is. Take an MP5 for an example. What is the capacity everyone is allowed? 15? 30? 32? 40? What about a 100 round beta box? Then there's the 60 or 100 round surefire mag for M4's.
Last edited by coach; December 12th, 2013 at 20:29..