The terrain in Afghanistan was even harder on Russian vehicles than they were on ours. There are hundreds of pics of broken down Russian tanks from their war in Afghanistan.
Siege vehicles just aren't meant to go through that terrain. It would be like asking a football defensive linemen to wear full body armor and hike up and down mountains. He's bigger and stronger than average but its harder on his internal structure. Someday a knee is going to tear. Or like Hannibal's elephants crossing the Alps.
m4s are alright as long as you clean them. All the time. Everyday. In Africa the magazine well would get clogged with a fine coat of sand, you'd insert your mag, pull it to make sure it was locked, walk about thirty feet and have the mag fall out on the ground. The dust would grip the mag like it was in place, but as you walk the dust would disperse and drop the magazine even though it looked and felt seated.
Just has differences to do with internal design that I'm not technical enough to break down for you and doctrine.
Some countries sacrifice accuracy for a heavier round that if it hits you in the vital area your dead like Russia with its 7.62, whilst the US uses 5.56 ammo for accuracy at the cost of stopping power. An m4 kicks like a .22 and has a round barely any larger.
We have heavier weapon systems like the m240 that can fire when filthy.
But the terrain in Africa is what broke down our vehicles and I'm sure the problem is amplified in the more rocky Afghanistan.
Part of the problem is the US military trying to save a buck. A lot of the first generation Humvees were the old soft side Humvees with the up armor kits added onto their frame. When you have the nut and bolts for something meant to hold together something way lighter, trying to keep them from breaking is a job just by itself. We couldn't even exit the vehicles and leave the doors open because the hinge kits were mean for Humvees with no armor and not made for a door holding four hundred lbs of armor.
Supposedly the last generation of Humvees were Humvees built with the terrain and armor kits in mind so they were designed to always carry the weight. We never saw them though.
The MRAPS were a little more sturdy but more dangerous. When we were training on them the training cadre would pull the gunners down out of the turret because if it rolled on a hill we were climbing and fell on its side, the weight of the turret alone could snap the bolts holding it in place and cut the gunner in half.
Meanwhile Army Special Forces are driving around in lightly armored Land Rovers and there little dune buggies not giving a f**k. The US military is more advanced than typical even down to the national guard level, but the true high speed shit is given to SOF and eventually their training methods and TTPs make there way down to us.
Soon we will probably sacrifice armor for speed as they all seem to be doing.
