To answer Pyro's questions:
1. I was told that I couldn't use the magazines by two range officers and both the old guys in the range office.
2. One of the range officers (the first one to talk to me) was new. After I told him that I was using a legal magazine in a legal firearm, he came back with the senior range officer. He and the other two were obviously not new.
3. Yes, they misunderstand the law.
4. Probably pretty good. They alluded to the fact that the AWB law was not popular and did not make any sense to them (their poor interpretation notwithstanding). They also mentioned that they had seen guys being hassled by local LEO (sheriff?) for using hicaps and that they didn't want any trouble.
All in all, I don't think that these guys were very "sophisticated" or willing to take the time to read the law themselves.