The spring looks correct from here. I agree about the goop being grease, could be axle grease which isn't even close to the right stuff. I'd put the trigger group together on the rifle and smack it with a nylon hammer. It'll release. The follower could be bent so your rifle doesn't feed, can't see... There's a thread currently about restoring a find like this...worth a look. He's going through what you will be. https://www.milsurps.com/showthread.php?t=59252