The Rem 74, 740, 7400, etc are very good guns. They are perfect as a bush gun for large game, and accurate enough for your typical bush shots of about 50 yards and under, but still accurate enough for a 100 yard shot if needed. 180 grain soft point ammo (silver tips) function through these guns nicely, and are a good round on large game.
The main problem with these guns is the chamber. You must clean the chamber using a chamber brush at the end of a day of shooting at the range, or when you get back home from hunting. Scrub it with the chamber brush, and then apply a light coat of gun oil directly to the walls of the chamber using a cleaning mop or some cleaning patches. If you don't do this, the chamber walls will start to rust over the next few weeks, and then pitt, and this is one of the reasons these guns jam. The jam is caused when the brass cartridge casing expands when fired, and forms into the rust and pitts on the walls of the chamber. This causes the empty brass casing to get stuck in the chamber enough that the extractor is unable to remove it from the chamber.
The other reason these guns jam is because of too much oil in the chamber, and in the action parts located under the forend (this goes for all semi-autos). Too much oil turns into dirty, sticky, carbon upon the first shot, because of the flame and heat from the round being fired. Carbon mixes into the working parts and causes them to not function smoothly, especially if you're hunting in cold tempurtures.
Oil is good on these parts after you're done shooting at the range for the day, or when the hunting season is over, and your rifle is going back into the safe. However, you need to remove as much oil as you can from the chamber and bore, and from all the action parts located under the forend a day before you start your next hunting trip. Just leave about 2 drops of fresh gun oil on the coil spring, and always best to make a test shot at your gun range before starting the big game season just to make sure all is working good and the sights are true.
So, if your buying a used Rem 74, 740, 7400 etc the first thing you want to do is lock the bolt back (mag must be inside) and look at the chamber walls with a strong flash light. If you see a lot of red specks of rust on the walls, and/or dark spotting (pitts), then I would not buy it. All though, It can be fixed by a proffesional gunsmith, but if the pitts are too deep, then it will need a new barrel at a cost of a few hundred bucks by the time the new barrel is bought, fitted, and installed.
I hope this info helps.
All the best.