I don't have the link it was a white paper on the M16 published on carbon paper in the 80's.
If you don't lube your weapon any weapon it won't function. That's a fact. You might get lucky and work without lube like Big Bore stated but would your risk your life on it? No run your weapon wet.
All piston AR and rifle that design similar to it has one big problem. Piston binding. The piston jam on the gas tube. Once that happen it's over because there is only one way to clear the malfunction and if that doesn't work you have to do a complete disassemble. Collapsed the stock slam it on the ground as hard and fast as possible and hope the piston unbind itself.
Unless it is a oversize gas tube like the AK the risk of piston binding are high.
Of course there will be less fouling on the bolt in a piston rifle because the gas is hitting the piston. The fouling will in the piston and gas tube as I pointed out many times. The fouling will be the same but in different location between DI and piston rifles. The fouling does not magically disappear on a piston rifle it just deposit at a different place.
HK416 in suppress mode jamming.
http://rpginn.com/index.php?option=c...=443&Itemid=39