I don't see how reducing the weight by 1/3 actually reduced recoil. If anything it should increase it. The stock changes could have reduced felt recoil though.
Other than the new receiver, muzzle brake, reduced rate of fire through the hammer mods, and the stock changes. They really didn't make that many changes. I would prefer a milled receiver if I had a choice simply for the added strength, and accuracy.
You stand not on solid ground my freind.
The stock is very important, look at the 47 stock, like classic rifles of old, it droops downwards because that is the most comfortable shape, but back then, nobody had considdered how that shape affects recoil.
Its newtonian physics 101, for every action, there is an opposite and equal reaction, so when you propell a projectile out of a gun, the gun is also propelled directly backwards.
But it is stopped by the shooters shoulder, so having the stock connect to the shoulder in a place that is below the barrel (the source of the force) as it does on the 47, means that the barrel will climb upwards violently, and yaw to the right (if you like most are shooting righthanded, since you hold your torso at an angle when shooting, that effects the direction recoil, the yaw).
On the AKM this was adressed, the stock is allmost in a straight line with the barrel, much like on the M16 family of weapons, and this drastically reduces "felt recoil" or "barrel climb", the force is ofcourse the same, as it is the same caliber and the same barrel leangth, but it is transferred to your shoulder in a way that is much easier to control, as it doesen't "bounce off" your shoulder in the same way, but is absorbed.
This is even true for the folding stock versions, again, on the 47S it droops downwards, but on the AKMS it goes in a straight line.
The front grip is also important, on the 47 it was again very traditional, but the AKM added "buldges" to the sides, so you have a much firmer grip on the weapon, its a small change that makes alot of difference when trying to controll a fully automatic weapon.
And lastly, but certainly not least, the AKM has a recoil compensator, that strange triangular muzzle break on it actually forces the muzzle blast upwards and to the right (which forces the weapon down and to the left, counteracting the weapons recoil), it makes a very big difference.
Add them all togeather and you get a drastic reduction in felt recoil.
Also, it is a mistake to think that the milled reciver is stronger than the stamped reciver, i can see why you would think that, but its just not true, infact the stamped reciver is the strongest because it is not as rigid, it will bend instead of breaking so to say, forces will bounce off of it rather than smash it.
The only reason you dont see milled recivers breaking is because they are so fricken massive! but it is redundant when you can make an even stronger reciver from steel plates an milled inserts, a total waste of time and costly resources.
Also, the milled reciver is not a more accurately machined part, the stamped reciver also uses milled parts to hold things in place, they are just inserts that are ticwelded to the basic shape (the steel plate), so that has actually not changed.