A question we get asked regularly by people new to airsoft as well as more experienced players is with AEG magazines and what is the difference? So we're going to give you a quick run down of the basics here.
There are several main types of mag and we don't mean that they fit different guns like M4 or AK or MP5, but it is usually all to do with the BB capacity (Cap) of the magazine itself. This is roughly broken down into 3 real variants - High (hi-cap), Mid (mid-cap) & Low (lo-cap).
High Capacity - Hi-Cap Magazines
These are commonly known as "Battle Maracas" due to the rattle sound when shaken. They typically hold around 300+ rounds (on an M4 mag), the BBs are poured in through a hatch in the top and to feed the BBs up into the replica, you have to wind a small wheel on the magazine base. You typically have to continually wind the magazine every 20-30 shots to continue feeding BBs up into your gun.
High Capacity Flash Magazines
These are pretty much the same as standard Hi-Caps, with one major difference being the winding mechanism. Usually they have a slightly lower capacity than standard hi-caps too (20-30 rounds). The winding mechanism on Flash Mags is by a pull cord hidden inside the base plate of the mag. Once you have filled with BBs it is just a matter of flipping the base plate down and giving the pull cord a couple of quick pulls, then the mag is pretty much wound for the entire capacity of the mag. It may be that you have to re-wind the mag part way through, but we have used Flash mags that manage to feed the entire load when fully wound at the start.
Middle Capacity - Mid-Cap Magazines
Usually used by more experienced players and those wanting away from the rattle sound of hi-caps. The magazines hold anywhere from 90-250 rounds depending on the make and gun platform. The BBs are loaded individually through the feed lip, the easiest and quickest way to do this is using one of the many different speedloaders available. As the BBs are held in a tube under spring tension, they don't rattle around and even better is that once filled, there is no wheel to wind up the mag, all the BBs will be fed into your gun simply by the spring system inside the mag. Eventually the spring will get weaker (especially if the mag is left fully loaded for a long time), on some makes of mags you can easily replace or upgrade the spring to allow you to keep using the mag without having to buy new ones. There are also some switchable Mid-Lo Cap mags on the market today.
Low Capacity - Lo-Cap Magazines
The staple of Milsim players and those wanting to stick to as accurate magazine capacity as possible to the real steel version. Typically most Lo-Cap mags will hold around 30 BBs, much like the real versions. These are loaded and used in exactly the same way are their mid-cap cousins, with the one difference being the much lower capacity.
Other than these basic variants the only other differences is the outer shells, either made of stamped metal or high density polymer, it makes no difference to the operation of the magazine and is purely a cosmetic option with various styles available.