The BB feed channel and base plate can be removed by gently pushing the top of the feed channel forward, and then down. At this point you can also remove the bottom plug of the gas reservoir. Tapping the main magazine body with a plastic hammer helps to pull it out by recoil force. Next we remove the top section of the magazine, which is held in place by two pins. It can also be removed most easily by the ingenious use of recoil. Please note that the valve lock can jump out, so operate in a clear plastic bag (or prepare to hit the floor looking for a small spring.
The most common problems in these areas can be remedied by taking care of the O-rings periodically. As with GBB pistol magazines, you can always tighten the fit with PFTE tape aka. "Plumber's Tape". It is wrapped into the groove to make the fit more tight, and silicone lubricant is then added as usual.
Both the gas inlet valve and the main valve should be removed with a proper tool to avoid damage. The main valve is bigger than normal, so some tools may need to have the cavity deepened. The gas inlet valve can be disassembled further by turning the brass inner tube clockwise. The injection tube will come out from the side normally facing out of the magazine, so it's a bit different than normal inlet valves.
The magazine is now disassembled for any maintenance you should need to perform. Looking at the parts separately, you can see that the magazine is not actually more complicated in terms of keeping the gas inside, compared to a regular GBB pistol magazine. The gas reservoir is a single-piece tube blocked from both ends by separate parts, and of course there are the mandatory inlet and main valves.
One of Western Arms' unique features has been the ability to fire a gas gun upside down without getting liquid into the main valve. The name of this feature is often mistaken as "R-Type", but the correct term is NLS, for Non-Liquid Siphon/System. It is not implemented in all pistols because of the volume limitation, but in an M4A1 magazine there's room to spare.
As you charge the magazine with gas, the long inlet valve controls the ratio between liquid/gaseous propellant in the magazine. This is necessary in all gas operated guns, because the BB is shot by the pressure of the gas, not the expansion rate of liquid into gas. After charging the magazine, the level of the liquid gas does not reach the intake tube, so you won't get liquid into the main valve no matter which way around you turn the magazine. This applies to any silicone as well as liquid gas, so adding silicone into the magazine with the propellant is not sufficient to keep the main valve lubricated.