Most AR pins are tapered pins and are driven OUT from the LEFT.
Buy or make a starter punch by cutting a standard punch off to about a 1/2 working length. You can also use a nail set.
The starter punch won't flex and bend and dissipate the force.
Next, get the barrel set up with wood blocks on a FIRM surface. A concrete floor works well.
If needed have a buddy help hold it steady.
If you strike the barrel and anything moves or bounces the force will be dissipated and the pins may distort and lock even tighter.
Inspect the ends of the pins. Since most AR pins are tapered, check to see which way the pins are driven in by comparing the ends of the pins to see which is bigger.
Once you get the pins moving with the starter punch, switch to a standard punch to remove them.