All that stuff's earlier in that chapter, or should be at least around 310.
C - clip (external ammo 'clip')
M - Magazine (internally loaded magazine)
The difference is that it takes a Simple Action to reload a Clip while a Magazine takes a Complex Action. Keep in mind though that unless the gun is a smartgun, expelling a loaded clip is also a Simple Action. If it's a Smartgun (or has the accessory) then it's a free action to eject the clip.
RC stands for Recoil Compensation. Look around p150 for more info on shooting and such.