:grin: Even though this post is a few weeks old , I figured this may help a few. I've taken several flash suppressors off other peoples' FS and here's the way I do it to save the barrel threads.....
I used a dremel tool with the cut off blade, I mount 3 blades on the spindle for thickness and stability. Under a magnified, I slowly cut into the suppressor parallel to the pin. I cut till I'm thru the pin. I then give the suppressor a shot of Kroils penetrating oil and the suppressor simply unscrews, with barrel threads intact. You can get a new suppressor from FN, if you ever want to re install it.
You have to be carefull and slow while performing this operation, but it really is a piece of cake to do.