I should have said ex military, former Infantry.
Farmer John,
In your defence we are further apart. I was Army Reserve, never in a combat area. Conditions in your photo I have not lived in, but when pushed through Canungra (Our Jungle Warfare Training Area) we were pushed hard, rightfully so, and crawled through conditions like that, also on various exercises. In no way am I comparing my time as equal your time in the service, and I dips me lid to you

. However I have put various weapons through those sorts of conditions and with standard cleaning none failed including some without the cleaning, namely our F1 submachine gun, and the SLR L1A1(Derivative of the FN). Still would not like to rely on non-maintained arms in a combat situation.
As you say most are not as temperamental as some make out, mostly. I will say the SR25 is, but boy they shoot.
I found at times some problems were because people over oiled their rifles and didn't wipe it off.
I have a Rem 700, one of several, in 375H&H and need to get a M16 extractor put on, only because it is one produced in the 90's. The first 700 I bought about 1977, on its second barrel and the extractor is still going strong.