SPEED Airsoft Tunable Trigger for HPA M4 Airsoft Rifles (Color: Green / Blade)

"Very well designed and as the other review said, very useful for an HPA build, ESPECIALLY if you have a Jack, F1, or F2.

The reason for those specifically is you can adjust the travel so that it's not limited by the actuation switch (i.e. slamming the plunger switch to its full travel) of the HPA unit, thus avoiding damaging the switch.

Additionally, you're able to get a much tighter and lighter trigger pull as well. I'm currently figuring out how to short stroke it with the safety engaged, and I hope that goes well.

Excellent product, and greatly increases the handling of your M4.

"i think you should buy this if you want to shoot this put this on my polarstar shoots very good recommend this to anyone

"This thing is AWESOME when you get it dialed in just right! Night and day difference from the stock trigger on my Krytac Trident MKII SPR with a Polarstar Jack installed. It did require very minor fitment to move smoothly and freely in the stock Krytac gearbox, I just had to slightly ream out one of the holes where the trigger's cross pin fits in the gearbox. After I dialed the trigger in, I shaved the safety lever a little so I could still use the safety while having the trigger essentially pulled most of the way.

Here's how I adjusted my trigger once installed:

Connect just the battery to the FCU. Don't connect air!

Remove the screws and put a tiny amount of blue loctite on them. It'll take a little time to cure so get right to adjusting.

Back the take up screw (front) out and screw in the over travel screw (rear) until it stops. Back the over travel screw out while gently pulling the trigger just until the gun fires (solenoid click). Back it out another quarter turn and test the trigger to make sure it fires every time. You can fine tune from there by turning the screw back in in tiny increments to eliminate more over travel while maintaining reliability.

Then without your finger on the trigger, turn the take up screw in just until the gun fires, and then back it out a quarter turn. Make sure it fires every time you pull the trigger. Again, very fine adjustments.

At this point, you're pretty well dialed in. You can fine tune both screws, a tiny fraction of a turn goes a long way.

I shaved my safety lever a little so I could still use the safety with the trigger dialed in the way I have it. At first the safety would not engage.

Overall, COMPLETELY worth the effort of fitting, installing and tuning. I can rip semi auto shots off very quickly, one guy thought I was using full auto!