I'm trying to take off a barrel out of an upper that I've had for years, and never shot a single round out of. I pulled off the barrel nut without any problems, but when I tried to pull of the barrel it was stuck. I'm using a clamshell receiver block, and put a 1'' pvc pipe into the upper and smacked really hard to try to force it out of the upper. Nothing moved. How can I try to get this out?

Update: I got it out by putting it in the freezer for 15-20 minutes, and then giving it 40-50 smacks with a 5lb sledge hammer, and a pvc pipe.

Try heating the upper first.

I have a Delrin rod I use,  You get a lot more surface contact then a PVC pipe. A wooden dowel will work too.

I put it in my  freezer for 15-20 minutes, then shoved the pvc pipe back in and gave it a good 30-40 smacks with a 5lb sledge.