Do keep in mind that broadheads basically always have paint or oil inside the ferrule, and those can definitely interfere with any glue bond. The best results I've had with Ferr-L-Tite involve cleaning inside the ferrule first. Heat the glue and swab some on the adapter (not heated). Next, I heat the broadhead ferrule and then melt the glue (on the adapter or shaft) a bit by passing it thru the flame a couple times. Quickly push the glue/adapter into the broadhead and rotate. If things are smoking or bubbling...it's too hot. If the excess glue acts like syrup...it's too hot. You should only be able to rotate the broadhead on the adapter or shaft for maybe 10 seconds before things set up. Check for good alignment, and use gentle flame heat to soften the glue enough to rotate or adjust the broadhead.
Epoxy-type glues, JB-Weld, etc work great, but with a couple qualifiers. When the glue hardens you have no ability to adjust alignment of the head and adapter, so get it right from the start. You likely can't remove the adapter easily or without somehow abusing the broadhead via excessive heat. This might not matter if you know for sure you'll never want to remove the adapter.