From one post on l1a1.com I read about Hesse's 50, I'd be wary. The guy posted pictures of the receiver, and it needed major work with a mill. I can't find the thread now, but I think he said he put over 50 hours of machinist time into it before he considered it safe to fire. I don't remember what he did to the bolt, but he did say it wouldn't close when he received it. The "bar stock" muzzle brake was actually cast, because you could see the casting voids on the surface of the part. Also, he had to enlarge the hole in it because it wasn't drilled straight and a bullet would have hit the brake (and would have turned the brake into a break). If you get one where the bolt will close and you look through the barrel and don't see any obstructions, you should be most of the way towards having a rifle that's safe to fire.
On a more positive Hesse note, I've heard of several people that put together FAL's on a Hesse receiver with less than a few hours of work on the receiver. That's not too bad. For the one I put together, I only spent a couple of hours modifying a barrel to fit the receiver. Also, the threads on the receiver for the barrel weren't finished well enough to screw the barrel on, but they were close enough that I could finish them with a cheap tap. The slots for the bolt carrier on the sides, while not cut deep enough or wide enough, were in the perfect position horizontally (unlike some of the original Hesse FAL receivers). The outside edge of the receiver was very rough with 0.03" (!!) deep pits on it. I don't know if the pits were from rusting or from casting voids, but they didn't affect the functioning of the receiver.z