No semi-auto will function when dirty, clean the action, gas system and gas port(s) in the barrel. Clean the magazine and lightly lube. Part of my job when I worked in Browning Arms Company's gunsmithing shop was working on BAR rifles. Most whose owners had sent them in complaining of jamming and not functioning properly were simply dirty. You can't neglect cleaning if you want a semi-auto to function properly. Also when I say light lube it only takes a drop or two to do the job, spraying with WD-40 or similar products is not advisable. Too much lube will attract dirt, you want only enough lube so the parts work smoothly.
