Still haven't defined extreme conditions. One would assume human life would still be possible.
The jammomatic era of the AR15 still lives for some, what they fail to know with a broader range of experience is that whatever could jam one, can jam them all. At that point, it's more the operator's fault. What should be considered is if they can withstand the extreme conditions over years at a time. Have they trained for it, keep in practice, and have immediate action drills down to where they can't get it wrong? Or are they the kind of guy who never check fires his gun before leaving the wire, and at the first sign of a stoppage they jam a cleaning rod in the barrel and split the open end on the ogive of the bullet, leaving it immediately useless?
A well trained individual can use any of the suggested weapons and get by. One not so well trained will find the AR at least is user friendly, reloads faster, gets in action quicker, shoots a little closer, and doesn't need as much maintenance as some think. It has more accessories, and the user can modify or repair it more easily, without expensive downtime at a gunsmith.
All the other guns require a smith press the barrel into the receiver and set headspace, the AR comes with a barrel extension anyone can install in an upper, and most run fine with anyone's bolt.
People need to worry less about the gun, and more about whether
they will be reliable operating in extreme conditions. Bluntly, most can't without months of general training and literal years of shooting practice. And you keep practicing until you can't get it wrong.
