strapwrench........OR if u rnt gonna use that stock feedneck ever again u could put the feedneck (make sure the body wont get scratched) in a vice and tighten it up real good and crank on that *****!
if u want like minor scratching on it u can put a towel around the feedneck
I just jammed my halo as hard as I can into it and when I twisted my Halo off the feedneck came out too. Took me a while to get the feedneck off the halo though Lol. But my idea was a success.