And because it is a Mauser, it is inadvisable to chamber a round except through the magazine, due to the extractor design.
Mauser bolt actions are controlled round feed as opposed to push feed. That means you can chamber a round while upside down, falling through the sky, or in any other desperate situation and not have the cartridge get away. The down side is, if one drops a round into the chamber and forces the bolt shut, it will damage and eventually destroy the extractor.
Professional hunters in Africa have strong feelings about controlled round feed vs push feed, but not all of them are on the same side. It's faster in an emergency to drop in one round and slam the bolt shut on it, but if you are dodging an angry critter and trying to reload from the magazine, push feed rifles have been known to lose a round on the ground.
Here's another idea for the 7.62x39--buy the cheapest old Savage, preferably with a short action, and rebarrel it. Now you can use up the 600 rounds, and you have a "switchbarrel" rifle. Anyone with average mechanicl skills can do it. http://www.savageshooters.com/ This site can provide all the info you need to make the swap. CB