The pins are tapered. make sure the pin was installed the right way.
When the pins are in properly, you drive them out from Left to Right as you'd sight down the barrel.
Some one "may" have installed the pin from the wrong side.
DO NOT just keep pounding on a resistant pin. All you'll do is deform the pin causing it to lock in place even tighter.
Here's how to remove resistant pins.
First, get the barrel in a well braced, "No bounce-No move" setup. If when you tap the punch the barrel moves, the force is dissipated and the pin won't move.
Use wood blocks to fully support the barrel around the pin. If necessary, get a buddy to help hold it.
The surface the assembly is resting on should also be firm. If necessary, put things on a concrete floor.
Make a "starter punch". This is just a standard pin punch cut off to about 1/2" to 3/4" working length. A starter punch won't flex or bend like a longer punch.
Once the pin is moving, then use a standard punch to remove it.
Use a heavy enough hammer. Light hammers give too sharp a blow.
