You are probably doing nothing wrong, i just got off here an A3000 LB and it's a real pig, so like you i wanted to strip it and got as far as you did and no further. I downloaded the manual and it says you really do need to put some force behind it, and boy do you. when you get to the point you think you are going to pull the whole pistol apart keep going, i recommend using gloves to save your hands. Mine did come off but i really can't believe how much effort you have to put in to do it. it was worth it all oiled and greased and the slide is lovely and smooth, though my donkey still won't shoot double action.
Hope this helps in some way.
atvb
Jason