Skip to content

Simulated 30 Round Magazines

A Trigger Master is modded to fire only 30 rounds from a magazine before requiring a mag change to “reload”. With this mod, a couple highcaps can simulate an endless number of 30-round magazines! As an added feature, the gun will not fire unless a mag is inserted, and tactical reloads (reloading before a mag is ’empty’) are possible. DOES NOT REQUIRE ANY MODIFICATION OF MAGAZINES.

This unofficial mod involves the following things:
– An M4 with a Trigger Master installed.
Custom Programming for the Trigger Master.
– A small switch installed into the magwell so that when a magazine is inserted, the switch is pressed.
Switch in magwell

How It Works

A switch is installed between AUX0 and GND on the Trigger Master. This switch is installed in the magwell such that magazines press and hold the button CLOSED when inserted. The button does not interfere with the seating or placement of the magazines.

(I got lucky and have a switch that was JUST RIGHT in my junk box. But since it’s a spare part I don’t have a part number or source for them. You’ll just have to find a switch that works for your gun as well.)

The source code for the Trigger Master was modified in the following ways (read the source code for more details):

  • Shots fired are counted down from 30 shots in a magazine. When there are 0 shots left, the gun stops firing.
  • Changing mags resets the counter to 30 shots. Tactical reloads are possible (i.e. changing mag before the 30 rounds is up to ‘reset’ to 30.)
  • Gun also will not fire if a mag is not inserted.

Known Issues:

  • 3-round bursts are always completed, and never partial. If we can start a burst, we finish it. In other words, if the shot counter is at 28 (2 shots left before needing a mag change) and we fire a burst, the burst will still be 3 shots (not 2) — and the mag of course will still be empty afterwards. Why? Implementing partial bursts was too complex to tackle for too small of an addition in realism. Maybe in the next version.
  • Shots fired in fullauto is estimated. This is because without installing an additional sensor we don’t actually know how many BBs are physically being shot out of the gun when a fullauto burst is made. The shots are estimated based on how long the fullauto burst lasts. It’s “good enough” accurate as it stands, though there is surely room for improvement.
  • If your magazine ACTUALLY empties (as in, no more BBs) this will not be detected by the Trigger Master. (Not unless and additional sensor of some kind is added.)


Source Code

Hex file