So first things first, I apologize in advance for the lack of pictures, I will post up some new and better ones the next time I rebuild my gearbox or do another hair trigger mod.

Keep in mind that you are responsible for modifying your AEG and I am in no way liable or responsible for any damages that can occur with and from this modification.

How to make a hair trigger for your AEG

So after years of playing airsoft with guns with ridiculously long trigger pulls I finally got sick of it. I have always been a fan of competition shooting and thought, wouldn't it be cool if an airsoft gun had a competition trigger feel? This is when I started my attempts at making AEG hair triggers. In the beginning I found out that all AEGS could be given hair triggers simply by adding a spacer in strategic points along the trigger. This worked to an extent; however, many issues popped up with this modification. First off, the actual starting point of the trigger would be changed, second the safety would be impossible to engage, third it ended up causing extreme wear and tear to the plastic sear on the trigger trolley, fourth it would have a full automatic dead-zone, etc.

So you basically get the picture, eventually I figured out how to do it right and this is the cumulation of all the knowledge I have acquired in creating a hair trigger.


Here is a video demonstration of this hair trigger modification on a dboys PDW which is the gun I worked on for this guide.

http://www.youtube.com/watch?v=9YB_HIosuvs


Keep in mind that this guide is for the advanced experienced techs out there and requires fitting. If you do not have any experience with airsoft modifications such as short-stroking, AOE, dremeling, and have a good grasp of how an AEG works, I would highly advise you to work a bit more with airsoft gearboxes before you attempt this modification.

This guide is for a Version 2 Gearbox, though the same principles are followed with all Tokyo Marui based semi-auto AEG gearbox designs.

There is a lot of back and forth fitting for this mod, be sure you have adequate time for the modification.

First off a list the things you will need.

1. A mosfet / relay installed in your aeg
2. Dremel with cutting and grinding heads
3. Pliers
4. 1/16" drill
5. 1/16" tension pin

(Optional)
1. G&G Trigger trolley (has the longest trigger contact out of all trolleys on the market)
2. Epoxy

Okay, let’s skip the gearbox disassembly process and go straight to the hair trigger part.

Remove the trigger assembly and the cut-off lever completely.

First make sure that the cut-off lever base has only a little protrusion when the cut-off lever is installed.

If there is protrusion as shown here dremel it down with the grinding head until it is almost level with the cut-off lever.



To this



(WARNING) Do not dremel off too much, or else the cut-off lever will be unable to move freely. This mod is done in order to ensure consistency with the semi-auto trigger engagements, in earlier tests I found out that the edge of the sear on the trigger trolley would get caught on different parts of the cut-off lever causing inconsistencies.

After this is done put the cut-off lever back into the gearbox, but note you will still need to modify it later on.

Take out the trigger housing without the trigger trolley inside. This is where the tricky stuff starts.

Take your pliers out and flatten the two prongs located in the trigger housing, then bend the top section of the contacts outwards as so.

If you do not wish to use a G&G trigger trolley you can also fashion your own trigger contacts out of sheet aluminum or copper, though it is far more difficult than just using a G&G trigger trolley.





Put the trigger housing aside, you will need it later on as it still needs to be modified.

Take out the trigger trolley, start by drilling a hole into the housing itself right in front of the plastic sear.

Insert the 1/16” tension pin into the hole. If the tension pin is too long, mark where it should end with a sharpie, and remove it. Cut the tension pin at the mark and reinsert the pin back into the housing.

The pin should be flush on both the left and right side of the housing, so there is nothing for it to get snagged on.





The next part is to cut a slot in the back of the trigger trolley so the trigger trolley spring has a slot it can fit into.



In previous attempts for a hair trigger, the trigger used to get jammed whenever you fired semi because the trigger trolley would get caught on the trigger trolley spring. This slot alleviates that problem.

Now starts the fitting part of this modification.

Assemble the trigger assembly completely.

It should now look like this.



Start by getting a multimeter and attaching the two probes onto the two solder points. (The locations are different on the PDW)

Switch the multimeter into the ohm resistance measuring setting; make sure that the multimeter reads infinite resistance with the trigger in the neutral position.

Start by manually sliding the trolley forwards; this is the critical and most important step in creating the hair trigger. The prongs need to be as close together as possible, but not close enough to get in the way and stop the trolley. This is also where the feel of the trigger is affected, if the contacts are too close together, you will have a very short trigger pull, but there will be a spike in the weight of the trigger pull half way through. If the prongs are further apart, the trigger pull will be longer and smoother.
Pick whichever one you like better or find a balance in between the two (my personal preference).

Next look at your gearbox from this angle, the semi-auto cut-off lever should be able to move up and down freely at this point. The white part circled in red is the semi-auto cut-off lever. The part circled in green is the tension pin you inserted into your trigger trolley.



If the cut-off lever cannot move up and down freely and gets blocked by the pin you installed in your trigger trolley, remove the cut-off lever, dremel off part of the sear, reassemble, and test again. Repeat as many times as necessary until the cut-off lever can move freely with the trigger trolley in the neutral position.

ONLY REMOVE MATERIAL FROM THE CUT-OFF LEVER IN TINY INCREMENTS (About half of a mm). IF YOU REMOVE TOO MUCH, THERE WILL BE A DEAD ZONE IN SEMI-AUTO WHERE THE GUN WILL FIRE ON FULL-AUTO.



Now, reassemble everything and test fire it!

Congratulations, now you have a working hair trigger in your aeg!

(Optional Steps)

One of the big issues with installing a hair trigger is that the safety no longer works allowing the gun to fire when the safety is engaged.

To fix this start by mixing some epoxy and applying it to the tip of the safety post.

Allow the epoxy to cure and then reassemble the safety.

At this step with the trigger in the neutral position move the fire selector to safe. If the safety post cannot move into the safety position, then there is too much epoxy on the tip of the post.

Disassemble the safety and the take a file and remove some material from the safety post until it is able to move freely from the semi-auto and safe positions.



Hope you guys enjoyed this guide.

This post has been edited by airborne101: Aug 22 2011, 08:16 PM