Was this a Stupid Question, with the lack of any responses I guess it was.
nope, ive seen in use basically smallarms, dont know about stuff regarding 203's/at4's or anything with high explosives... might be worth pming Argyll, hes a pmc whos been to iraq before he will probably be able to help if you explain your reasons why you want to know.
The restrictions are up to the company. At least in the US, PMCs fill out export style end-user certificates when buying equipment, allowing them access to pretty much whatever they have the money for.
Theres no restriction on weapons nor are they limited in using fmj ammo like the military is. Theres even cases of them using frangible APLP ammo and in one case shooting an Iraqi in the rear and was torn apart from it and is virtually untreatable. Nasty stuff that would have got a soldier court martialed, but highly effective.
Contracts I have worked would not let us go beyond a 5.56 round meaning M16 and SAWs, AKs were also in use. That does not mean we did not carry contraband. In the early days it was anything you could find or whatever you could get the Army to trade with you, grenades, AT4s... There was also a lot of arms for sale on the black market. Now due to liability and strict rules of engagement you carry what your issued. But like another poster said it depends on what your company gives you. Also, we had a free ticket to modify our weapons all we wanted.