You're not alone. I wanted to set up my 16" for a suppressor, so needed to remove the FH that was on it to replace it with a suppressor-ready FH. I kept researching thread direction for my type of barrel and FH as I couldn't break it free. I finally said screw it and started loading it up in torque in each direction, slowing increasing torque as I changed directions so I wouldn't overcrank it the wrong way. Figured if I couldn't break it free with the hand tools I was using, then cutting it off was the next step.
Imagine my surprise when I BROKE the FH in half - and a collar remained around the barrel where it was finally apparent that it had been "glued" on with high strength Loctite of some sort. Grain structure made it appear like a cast FH made to look like one of the factory threaded FHs - I wasn't torqueing THAT hard on it (I don't think
).
I'm of the thought that someone had modded it via the cheap route for making a shorter barrel from a full-sized barrel (the crown was really ugly and looked like a hacksaw had been taken to it).
It turned out fine as I had the muzzle threaded and crowned (and still remained over 16") and it ended up shooting surprisingly accurately for an FAL.