My buddy had two riot models, one with convential stock and one with a pisto grip. Occasionally we'd get failures to fire from what appeared to be the gun not cocking despite racking the pump and chambering a new round. Seems that you needed a rather vigoruous motion to ensure that it cocked properly. He didn't seem to have a problem with it but other shooters that day did including myself anf I do a lot of pump gun shooting with everything from Winchester 1897's (that need a rather vigorous pump themselves) to 500's and 870's.
I dunno, I know others have been happy with them but for the modest price difference I'd opt for a regular 500 or a used Winchester or Remington instead.