Please point out this code as I'm sure many here would like to see it.
I write programs for a living.
It would be so much easier to just have the fleshpound always immune to decapitations.
There is no way a fleshpound would be always immune to decapitation EXCEPT during a short window when his head is exposed while he is performing his attack animation - and someone is up there attacking at the exact correct time to take advantage of it UNLESS someone went great lenght to put in that code.
Someone put in that code on purpose. To give flehspounders a weakness.
This give berserkers (chainsaw have a fast rate of fire which make it easier to decapitate) and commando (bullpup have a fast rate of fire which make it easier to decapitate) a reliable way to deal with flehspounds as both of them have too little ranged damage per second to kill them before they get close.
Fleshpounds take half damage from anything else but explosives, this make nades and LAW twice as efficient against fleshpounds - this programmed "weakness" give give support spec a way to kill them before they get close.
A sharpshooter can kill it using 2 xbow arrows to the head (easy to nail one while he is far away to enrage it and one right after he stand up during his enrage animation) and 1-2 deagle shots (in a 6ppl hard game). On maps with some visability (such as london, farm or mansion) - I do that all the time (killing all sirens, fleshpounds and scrakes before they reach our camp - while the team clear out all little zeds before they get close to me so i can focus on my sniping).
A FP that auto-enrage will stay enraged until he reach his target and hit it once. After that he will leave his enraged state and only enrage if you damage it too fast or if he auto-enrage again. This give medics a way to kite him. Once he auto-enrage, run from him while you unload as much as you can into him. Once he reach you, stop shooting, bring up your knife, let him hit you once - outrun him. Heal up, let him auto-enrage again.
He used to not enrage by little damage, which was the flamebug weakness. Flamebug set him on fire and kite around while setting other stuff on fire. FP die from burnouts. This weakness have been removed though, because it was used by all other perks too efficiently as it promoted solo kiting on some maps (such as farm). Since the change kf became a bit more of a co-op type of game again. But now flamebugs really have no efficient way to deal with fleshpounders anymore....
The Big man got weaknesses. Learn to master your perks and you will find out ways to deal with him. Use your perk to the best of your advantage.
Decapitate at melee range, atleast if the FP is enraged, is still really dangerous. Atleast on hard/suicidal. A decapitated and enraged fp will still often hurt or possible even kill you. You might also miss the sweet spot (i find it hard to always land my shot while we are on uneven ground, such in a slope or a staircase) or the window of oppertunity (if you dont have a bullpup or chainsaw you have to time that single attack at the exact correct second). As i described, most perks have ways to deal with him. Up close melee decapitation-style if you are any other perk then commando or berserker should probably only be a last ditch resort.
Once again, this is not a bug. It is a build in feature of the game that you can use.
Shrug.