When my Father came through Liege not long after it was freed from the Germans, he said the plant was already taking orders from American soldiers for shotguns.
If the soldier paid, they would mail the gun to American once the guns were produced. Probably all kinds of laws now to prevent that.
The FN plant did assemble many guns for GI’s out of existing parts, but the Nazis had looted most of the machinery when they pulled out. Interestingly FN got a contract to refurbish US military arms during the final part of the war, as well as producing jerry cans and some small tank parts.
Here are a couple threads about the “Boudinot” gun, a Browning A-5 made for and given to the officer that liberated the plant. There’s a photo of an FN honcho making the gun in the basement with him standing in the background. They were under V-1 attack at the time.
http://www.shotgunworld.com/bbs/viewtopic.php?f=53&t=104926
http://www.shotgunworld.com/bbs/viewtopic.php?f=53&t=109584&hilit=boudinot