I was not keen on hammering the end of my barrel, so I used a cutting wheel in my angle grinder to remove the stock f'hider.
¡BLASPHEMY! ...anyway...
First I removed the front sight, just to get it out of the way.
Then, I wore through the back edge of the bayonet lug base... the thing to remember is TAKE YOUR TIME and RECHECK YOUR PROGRESS FREQUENTLY. I dreaded even a touch to my barrel with the wheel (thinnest cutting wheel I had, btw), so I took quite a while, pausing to let heat dissipate and to check how close I was getting.
Once the bayo lug was thin enough, a twist with a suitable screwdriver and it cracked. Further CAREFUL grinding thinned out the opposing side (front sight base) so I could basically bend and snap off the slotted section of that pos lopsided Norinco FH.
The castlenut was easy to remove with a leather padded visegrip.
More CAREFUL grinding/cutting thinned the back half of the FH splined section so with the same twisting a screwdriver trick I could crack one side, wedge farther open (breaking the welds), and then it was easily threaded/pulled off. As I recall, I chose to thin between splines.
The trick of course is not to rush the job. I took quite a while, and have steady hands, even with an angle grinder. Most of the hour (maybe hour and a half?) this took was due to the FREQUENT RECHECKING OF THE WHEEL'S PROGRESS, as I was not remotely interested in nicking the barrel...
Your personal experience might vary with this technique, and if there's a frig up my bet's on that the job was rushed.