For a gunsmith the Remington pump/semi-auto hunting rifles (760/740, 7600/7400, Model Four, etc) are pretty simple rifles to disassemble, they're not "spring bombs" like some guns are. 

For many gun owners, they're not so easy because you need a few tools you usually don't have, starting with a roll pin punch. Most casual gun owners do not have these.

I'm attaching the owner's manual for the 7400. 

If you look at the exploded diagram on page 14 of the manual. To remove the trigger group, you drift out pins 72 and 73. To remove the foreend, you remove the screw "28," and then pull the foreend off. 

From here, you could pull the bolt back and be able to hose down the bolt and the gas system with carb cleaner, and then go down the bore with a bore snake or clean the barrel from the muzzle with a rod. Then I'd hose down the gas system, then lube things up and put it back together. 

If you want to disassemble further, you need to get a couple of roll pin punches to punch out the roll pin in the gas block ("5") and release the gas tube, and another one to drift out the roll pin that holds in the bolt handle. Most people don't have roll pin punches - they look very much like regular punches, except they have a little bump on the face of the punch to keep it centered in the roll pin end. 

There's a nut that holds the barrel into the action ("8") which holds the barrel into the receiver. 

There's another roll pin in the bolt (I think it is "43" on the diagram, but I cannot be certain) that needs to be drifted out so you can remove the bolt handle ("42"). To do this, as I recall, I had to position the bolt "just so" so that I could get at the pin, and drift it downwards. With that pin out,  you can slide/wiggle the bolt handle out of the bolt, and with that done, you can pull the bolt out of the front of the receiver.

For most gun owners, I would recommend not drifting pins out, and just doing the most basic of disassembly to open things up so you can hose it down with some spray cleaner. 

remington_7400.pdf (508KB - 14 downloads)