I could not find much about the US Army "Dust test" other an a wiki reference to the limited 6000 round test between the HK416, the FN SCAR, the XM8 and the M4.  It has been said that the M4 did "significantly  worse" on the dust test than any of the others.  What was the root cause of the failures?  Was it the DI system or something else?  Seems like the only difference that made the M4 stand out is all the others are piston guns.  



Not trying to start a DI vs Piston food fight, just wondering what the root cause of the M4's poor performace was.

Also, Anyone know what US Mil units are using the HK416?  A buddy of mine just got back from Iraq and he said some of the units there were issued w/ the HK's.  Just wondered what US units were using them.

I saw the article also, saw another article, sorry do NOT have it, that the test articles (weapons) were supplied by the manufacturers with before hand knowledge of the test, except the M4's which the Army randomly selected M4's from their inventory.  Take it with a grain of salt.  This is NOT the first report we've seen the M4 suffers more stoppages than other rifles, NOT saying they are bad, just that there has been reports the stoppages are higher than the M-16 or other rifles. IIRC, the test was pretty extreme with a special chamber that dusted the weapons before they took them out into the desert to shoot.