Just picked up standard weight browning A5 12ga early 50's build I believe with a 28" (actually 27.5") vent rib barrel and modified choke. During disassembly for cleaning I was amazed at how easy it was to unscrew the mag tube from the reciever. I greased the threads on the mag tube upon reassembly. I noticed that even with the set screw threaded into the mag tube that I can ever so slightly twist the mag tube. I really have to put some force on it to make it twist. Is the mag tube supposed to solid with no movement? Should I have used a thread locker of some kind? I can see where if it was really loose it'd be bad. But this ones not that way. Other thing I noticed was that there's a hairline crack about 1" long on the forearm just in front of the reciever. It's superficial though as it doesn't go through the forearm. It's just on the exterior. Not sure if I should be worried about it especially since it doesn't go all the way through. Should I break out the acraglass now or just see how it does?