Have had this idea for a long time, but kept putting it off. Finally decided it's time to experiment.

The goal: Design a new safety selector that will provide three options (Safe - 2 stage - Single stage). The first two would be as you'd expect, but the third position would essentially remove all of the first stage from the equation. Making for a trigger pull that is short and with reduced weight.

Where I'm at: Found a trigger jig on the interwebs. Printed it up without needing any supports and it came out pretty clean (3.5 hours). Found an M16 safety selector. Made a couple tweaks so that it'd print easier, and fired that off as well (20 min). Grabbed a Larue MBT 2s trigger and a Magpul MOE grip from the parts bin. And damn, it all went together like a glove.

Looking at the mechanics of a bit this afternoon, I've got two ideas now on how I can remove the take-up for in the third selector mode. Unfortunately, I broke the jig dry firing it. I guess that's one downside of printing it in the upright orientation. All the layer lines are parallel to the where the hammer impacts. So that much force is just asking too much of a print.

Printing a new one up now. Same orientation, because it turned out so good last time. Will just be cognizant of not letting the hammer fall with its full force (just like if you were dry-firing a detached lower). I will try to print one in a different orientation later (layer lines running perpendicular to the hammer's inertia). As I think that'd increase the strength significantly. But right now, I'm more eager to start working on my potential solutions for removing the take-up.

Forgot to get a pic of the trigger installed. Will snag one when this next jig finishes printing. But it basically went together like a normal lower. I did quickly ream out the safety and trigger pin holes slightly (3/8" and 5/32" respectively). But everything was still nice and snug and went together without even needing to use punches.

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Tag.


Good work here

Thanks! Got the other one printed up and did a little CAD work in the interim. Where I actually came up with a third idea that may be the winner.

Right now doing it specific to the Larue. But I may be able to adapt it to my Geissele triggers as well. As their design is quite different.

Just need to see if the selector design on paper works in application. Stay tuned…

Probably even just a good idea to have on hand for stuff like doing trigger jobs.

Where did you find the files for the trigger test jig? Is it your own?

Exactly. Just might need some modding if you intend to let the hammer fall with its full force more than a few times. I’ll also update when I print one in the horizontal orientation to see how much (if any) difference it makes.

As far as the jig, it was a file on Defcad. But I don’t personally have a membership. So I did a Google search for “trigger jig STL” and found the same exact jig for free on Prusa’s community website.

@Deerhurst

I'll take a look! Might already have the files. Got a hard drive full of 2A stuff I'll have to scroll through.

Played around with it yesterday evening. And it works!  

Now to refine and fine tune…

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thats a cool project OP

I used a standard full auto selector file for a starting point. As I wanted the three position component of it. But that’s about the extent of what’s original.

Have made a number of tweaks and iterations. Even adjusted the detent locations for the three selector positions. Got it to a point where it functions as intended. Currently doing some tolerance testing.

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You got it

Little bit of an update. Fine tuned quite a bit and tested a handful of different things to "pre-load" the first stage of a Larue MBT-2s. It definitely works. Which is pretty exciting. Although I haven't done any live fire yet. But I don't anticipate that'll change anything.

However, being kind of OCD, I've modified the trigger jig to accept a dial indicator attachment that I designed. In short, I want to be able to add actual values. Beyond just knowing by feel (and the eye test) that the take-up has been reduced. Printing now and will be waiting for me in the AM. Then I plan to test the following with my dial indicator...

1) Full 1st stage take-up in the traditional fire position
2) Take-up and reset reduction with the "pre-load" fire position

Once I have a target for the value, I can continue to refine and chase the greatest amount of take-up reduction. While also retaining 100% functionality. Upside is that I've compared the Larue to my Geissle triggers, and I think the solution I landed on could easily be retrofit for the G triggers.

For now I'll need to do all the testing with a 3d printed selector. But, at some point, I'll probably need to enlist a machinist to actually make one out of proper materials. So if anyone has suggestions on that front, I'm all ears .

One other question / point of feedback from the hive...

So, the best (current) solution I found requires that the 3 positions of my selector be different than a full-auto selector. In that the "pre-load" mode is 180 degrees opposite the Fire mode on a traditional selector. Hope that makes sense. Basically have to flip the selector upward (from safe) for "pre-load" mode. While downward (from safe) would be the normal Fire mode.

Can anyone think of issues with this? Aside from that some just might not like it that way.

I might be able to configure it as a 0-45-90 selector. But the method I've currently landed on just won't work in a traditional 3-position / full auto configuration. I'm definitely going to play with some alternatives. But will likely need to get even more creative than I already have.

Modified trigger jig and dial indicator attachment are done. Had designed the dial indicator portion to accept a cross-bolt for tensioning. But it's really snug as is. Maybe could have been a little more elegant. But will work for my needs .

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Got some additional components delivered for the "pre-load" testing. Starting to feel like I know what I'm doing.