Isn't 33% hits at that range a very good result for somebody who has not been to some kind of special school?
Getting hits @ 500m with a SAW is nothing special, especially if one in the prone. The SAW, in my experience, is a very accurate weapon - as accurate as the M16A4, a weapon with which it is hard to NOT score 8/10 or better hits on a USMC KD range @ 500m with iron sights.

The other problems with the SAW (weight, maintenance issues, the inherent issues with an open-bolt belt-fed weapon) exist to a more or less manageable degree, but in my experience accuracy has never been a SAW problem.