I agree that the test was internally inconsistent. But focusing on the M4 alone (leave all others out of it), the data show a significant number of failures. The SCAR and XM-8 results I pretty much ignored, since we’re not going to bother with those. The DOD simply doesn’t have the money to field a new infantry weapon. They’re too strapped for cash in the current situations.
The argument that “the dust was extreme” and would not be encountered — well, perhaps. Maybe. Most people haven’t seen a lot of dust in their operations of firearms. Living in central Nevada, in a farming area, where we have lots of blowing dust that is as fine as (or finer than) talcum powder... I’d have to say that many people haven’t seen the wide variety of dust that there is. And our alkaline dust fouls AR-15s quite nicely. M-1A’s work wonderfully well, as do simple blowback actions like a 10/22. Bolt guns always work.
AR-15’s spend a lot of time in gun cabinets, which is a shame, because the coyote situation around here calls for an accurate (check) .223 (check) that is semi-auto (check). It just has to fire when you want it (fails).
Much as the Eskimos have hundreds of words for snow, folks who live in deserts have umpteen types of dust. My question is “does the military involved in spec’ing weapons know how many types of dust there are?” and I’d bet the answer is “probably not.” So they substitute quantity for quantification, and you get what we have here.
A bit more on the M262: It is loaded rather hot, above SAAMI specs. The M4’s big contribution to this was tightening the twist to 1 in 7. This, I suspect, was a contributing factor to case failures in the testing.
Here's a little bit of data for you to peruse. Notice the initial 07 testing of the M4 yields a similar failure rate as the HK416.
What is not answered is the question of whether the M4's tested in the fall of 07 are the same ones tested earlier in the summer of 07. If that is the case, which is most likely given the Army's way of testing, it put that particular group of M4's even further down it's end-of-life testing resulting in the disparity of the two M4 data groups.
My personal experience with the AR system is in a number of different environments, from sub-zero,wet,icy conditions of Montana to hot, blowing dust conditions in the deserts of New Mexico, Arizona, and Nevada have given me a good insight into the limitations of the system. When maintained, it works.