A reasonable upper limit to your pack weight is based on 1/3 of your weight and in a pinch 1/2 your weight. Understand packs at that weight you will move very slow and will burn a huge amount of calories. It is useless unless you have to move a short distant. No 160km/100mile E&E with a pack like that.

It is true in the army packs often got heavier, but mostly just before an attack when extra ammo was issued or for the unfortunate radio man. Carrying this weight is also something that required a high level of fitness, lots of training, and a whole lot of drive! normally with heavy weapons we traded off when possible and shift platoon gear around to even the load.

In the arctic my pack was always that heavy, but we never got more that 12km on foot in a day and at -40 we were reduced to 15min Walking followed by a 2min break to cool back down, instead of our normal 55min forced march and a 5min break.

Conditions, Fitness, and the Situation will dictate what you can Carry in what circumstances. Be realistic and if you want to carry that heavy of a weight in a pinch, them add 4kg/10lbs to the total weight and go out an practice with it and see how far you can go!