[archy]

2. Design the internals to reduce their sand-and-dirt sensitivity.

As for the cleaning issue, that's a training and mindset thing. I'm interested here in the actual weapon itself.

So, what are some ways to effect #'s 1 and 2 above?

Internal sand cuts, as mentioned in my response above, and as used in the British L1A1 version of the FAL and as helical cuts on the bolts of the L2A3 Patchett/Sterling 9mm SMG; similar *ribs* are seen in the external machinework of the rectangular bolts of the Israeli Uzi and the Ingram M10 and M11 SMG. Of questionable utility on some designs, but certainly usable on some. And more feasable nowadays with modern CNC machine tooling techniques, and even moreso on such injection molded plastic or investment cast components when designs call for such materials.

[Long Cut]

Thank you for the well-considered and informative answers.

Now let's hope the designers of the new rifle also think about this. Here's to hoping they actually talk to those whose boots get dirty from time to time about what THEY think they'll need.