on a 14" bbl ar the flash hider needs to be permanently attached for the 16" legal length. What is considered permanently attached. i.e. weld, silver solder, soft solder ??

I'm not sure, but a few years ago in Illinois the cop whose wife disappered was charged for taking the flash hider off of the barrel and making it too short. I'm guessing it was pinned not welded.

Pinned and welded is how we have done them. Others gave just welded them.

I know when I bought my Bushmaster and wanted to change the barrel, I found out that the flash hider was both pinned and then welded from the factory.