Uhm..
MRSPY wrotten in obviouser words..
He found a glitch/bug/cheat that lets you switch to your primary weapon's ammo while using the Secondary one... this can be used with the M79 and some kind of SMG.. That makes the M79 have 30 bullets in the 'clip' and 200+ in the 'stock'.
You can do this by pressing Reload a shitload of time and switching to the other weapon at the same time... May work with the grenades too , maybe.
Overall about the game... very nice.