i just did the same thing with my ar and had no problems disassembleing it to re install the firing pin.
try this. cock the weapon and if the bolt doesnt go all the way in take the weapon and hold it by the sock and firmly thump the flash hider against the floor. that should make the bolt fly forward enought to open the take down pin.
try this. cock the weapon and if the bolt doesnt go all the way in take the weapon and hold it by the sock and firmly thump the flash hider against the floor. that should make the bolt fly forward enought to open the take down pin.