u/YourBroStevo

Been working on this yesterday and today and finally have a functional prototype that works within the lower. This is a great sign and shows that it is possible to reset the trigger and install a force reset device with it. There’s still a ton of work to be done as far as setting up the housing having it lock in properly then dealing with how the FRT will interact with the bolt and all that stuff but at least there is some hope that it is possible to add an FRT to the factory trigger. This device would be FRT only and hopefully will be easily printable and inexpensive to make. Just figured I’d show off what I was able to come up with. There’s definitely a possibility that I’m unable to get it functioning with the upper installed, but I won’t know that until further along and development so fingers crossed I will have something functional soon, and I won’t run into any issues.

File is made public please don't ask in the comments where to find it respect the rules.

I was looking for something I could use as a tool to show how the drop in FRTs function, found this one and decided to modify it myself to be even more useful with FRTs. This is an amazing tool for somebody who's either cut their own trigger for the super safety/arc fire and are having a little trouble or is trying to size a drop in, which it simplifies greatly.

To make it useful with the drop-ins, I have cut out a window in front of the safety, so you can see exactly where the activator leg presses on the trigger, which will allow you to properly tune the length and create the small amount of free play I'm always talking about, all without having to assemble the gun. This is also useful for tuning the semi, since you can see how far forward the activator pivots and will be able to shave down the backside of the activator leg, exactly where it's making contact with the trigger.

For a super safety or similar, you have a great view in front to see exactly how the trigger cut is lining up with the cam. In the released version I have also cut a hole at the bottom behind the safety, so that you can have a very good view of the cam itself and see exactly how the trigger is slotting into it. This should be useful as a diagnostic tool, especially for determining exactly what part of the trigger you may need to remove material from if you have a rough trigger pull or safe in FRT. I've also added a hole in the back that allows you to attach rubber bands to hold down the trigger so you can test out the FRT function and have both hands free.

The final version isn't the one shown in hand and has a larger window, cut out at the bottom, clearance for an ambi safety lever and is slightly extended in length so the rubber band pulse harder on the trigger. Final version is shown in the last photo.

Works great as a regular trigger tester as well, and can be dry-fired repeatedly even just using PLA+. This is just a small project, but figure I'd put it out there in case it's helpful to somebody.

All files are publicly available. Please don't ask where to find them. Please respect the rules and don't ask in the comments.

These designs were made by me with some help from Eugenestoner18. Kabuto definitely deserves credit for his original design which I used as a base for mine. Compatible with the listed triggers, even the ones you may have overcut for the super safety.

Happy to finally present you guys the U-DIS (universal drop in system). This is my attempt to improve the Kabuto drop-in by allowing for aftermarket trigger support, proper sizing, M16 safety compatibility and multiple other changes to reduce any possibility of binding. When properly set up this is the best printed FRT and potentially the best FRT for aftermarket triggers particularly the two-stage ones. With this FRT there are no changes or cuts needed on the upper, lower, trigger or even the safety in most cases. Even the need for an external lever blocker is removed with this design giving it true drop in capabilities without making any changes to the gun.

I've owned and modified numerous drop-ins and unfortunately none of them currently offered are set up adequately out of the box. In addition to certain vendors bashing the original design and coming out with their own proprietary ones for extreme prices just to sell the M16 compatibility. With the current options falling short and a lack of innovation coming from any of these vendors (especially aftermarket trigger or lever blockers) I've decided to fix the design myself and put it out there for everybody to have for free.

This was designed entirely around the idea of giving the end user the most compatibility and reliability FRT I can. No choices were made based on ease of production or to maximize profits, so that the focus can be on providing everyone with the best FRT I can. Real tired of seeing people spend hundreds of dollars on FRTs and pre-cut triggers for them still not to work out and requiring end user modification. To me it seems like aftermarket triggers are an afterthought and are thrown in because they happen to be compatible rather than the FRT being directly made for them. For me they are the priority and one of the biggest advantages of using an FRT is that you aren't stuck with the mil spec trigger.

This is the only option offering you the ability to customize the FRT to your particular setup. All other devices are a one-size-fits-all and typically require you to fit the gun and trigger to the FRT rather than fitting the FRT to the trigger. To me most people would prefer not having to modify the gun or trigger and that all changes be made on the device itself which is what this offers.

In order to achieve this there have been multiple changes made to the activators and housings to make them compatible with Geissele, LaRue, milspec, Schmid two-stage, CMC and rise armament triggers. With the ability to pair them with KAK 3 position or an M16 safety with slightly modified (3 min with Dremel), depending on the trigger. I've also included the M16 compatible activators, so you can have that capability without the usual "BS" that comes with it. I have also made it pretty solid Ambi 60120 safety that works with my activators for those that would prefer a shorter throw.

Hopefully this allows people to use the triggers they want to and realize just how it inexpensive a solid FRT can be when you aren't forced to make everything out Hardened steel and inflate the price. Hopefully this helps lower the barrier of entry into the FRT game and makes it, so it's a no-brainer when you can make one for around a dollar and don't have to make any changes to the gun.

I have probably spent around 50 hours working on this from designing, to printing out hundreds of activators and test firing each of these setups. I wouldn't be surprised if these designs are worth thousands of dollars to the right person, but fortunately for you guys fixing these problems and offering a solid FRT that's extremely cheap is more important to me than money, so the designs are free as they should be.

No commercial use at this point. If you would like to sell part of my design or the whole thing message me maybe we can work something out. I don't care about money, I just don't want people to get ripped off and overcharge for something they shouldn't.

If you have any questions or need help setting it up shoot me a DM I'm happy to help or make any slight changes that you may need. If you've been on the fence on getting into 3D printing, I definitely recommend it so many possibilities and it'll save you a bunch in the long run. Hopefully this saves you the headache and some money over the other options available, and you end up with an FRT that's custom fitted to your setup. 

Testing out some changes I've made to my design in addition to the new trigger. It's definitely possible to use the drop in FRTs with single stage triggers, but it really does seem optimized for the two stage and that's where it really shines. Definitely cool too be able to have such a light trigger be compatible. Don't think I have seen one that has a lighter pull weight than two and a half pounds, so definitely one of the lightest.