Matrix Battle Axe 2200 Round Auto Winding & Sound Control Electric Drum Magazine for M4/M16 Airsoft Rifles (Model: Standard AEG / Black)

"Best thing I purchased for my m4. This mag is awesome. Easy to fill with side access panel that is right next to power switch. Off is in the middle, auto to the left, and sound activated to the right. Installing the 9 volt battery is easy just gently lift on battery cover that is located on the back of the drum (it at 10:00 o'clock) also marked with a voltage symbol. This fits my specna m4 perfectly, the sound activate mode is the best it keeps up with 2200 r/m. No problem. Can't wait to get it out on the feild

"OPEN FROM BACK!!!
There are 4 plastic locking clasps surrounding the drum that can be lifted ***FROM THE BACK*** with a flat head screw driver. Other reviews mention opening from wrong directions and I marked up my mag pretty badly.

Things to take note of:
- There is no user manual or guide of any sort for this magazine
- Holds 2000 rounds with ease but needs to be shaken around to fill it
- Rechargeable Energizer batteries usually die before magazine becomes empty so I carry a spare on me for in game incidents
- Battery compartment is secured by one of the overlapping side clasps, easily removed with Flat Head Screw Driver
- Does not come with batteries, highly recommend multiple reliable rechargeable 9V batteries
- For reliability purposes, I usually run on Auto, not Sound, though the option is available

This is by far, my favorite magazine to use. After 20,000 rounds, it has only jammed on me twice (after about 15,000 rounds) but a quick DIY fix of pushing an extra BB forward in the feeding wheel has fixed every jam in the feeding tube so far. Works great with my folding stock on my G&G ARP556 3.0 but does interfere with it leaving about an extra one inch gap from the frame. No more reloading for me. I still carry a generous amount of magazines on my belt just in case anything happens to this drum. Light up the field or arena with tracer rounds and send a message that everyone can see :)

"Great drum mag for the M4/M16 platform! Feeds really well and fast, and keeps up with my 30+ RPS m4 build with zero issue. Build quality is great but there is one thing that I hate, this came with no instruction manual so I had no idea how to get to the battery compartment to install a 9v battery. All the documentation out there for this mag is for the old version which has the battery located at the bottom of the mag, but this new one, it's now located at the top of the mag. After trying several ways to get to the battery, I broke the selector tab, and was incredibly frustrating as this all could've been solved with a instruction manual. So to get to the battery, one of the tabs on top of the mag,has to be pryed open, preferably with a screwdriver because it is an incredibly tight fit. Though I don't have a selector switch anymore I can still change the mode with a key which is not too big of a deal considering how well this mag feeds.

If it came with an instruction manual and I didn't break my selector switch it would've been an easy 5 stars. But I have to knock off a star due to the inconvenience.

"Matrix battle axe auto winding drum magazine
First off, the parts of other reviewers complaints of where to put the battery are spot on, difficult to determine what to do to access the compartment.
1) Looking at the back of the drum in the vertical position, there are four ribs surrounding the drum. The upper left rib has a lightning bolt next to it.
2) Using a large flat head screwdriver or a coin, insert into the slot between the rib and the lightning bolt.
3) Pry up on the rib and rotate the rib (cover) out of the way.
4) Install the battery and be mindful of the wires.
5) The cover (rib), has a curled end at the front connecting point, it is not a push in clip. Connect the front hook and then rotate the cover down until it clips on the back side.
6) AUTO is constant, middle is OFF and SOUND CONTROL is switch the other way.

That said, my initial trial was not impressive. The sound actuation didn't rewind until my gun shot blank, so every four or five shots is dry fire. It may work better on a gun with a louder shot sound but kinda annoying being that it will activate with the sound of the bb's rolling around but not when I fire a shot.
Loose fit in my gng war machine m4.
Small fill port and in an awkward location.
Small switch and indications.
This thing seems like it was designed by an engineer and not a player. Hopefully that means it will last.