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Old June 5, 2018, 06:53 AM   #1
Join Date: October 18, 2017
Posts: 17
DIY Binary Trigger

A binary trigger for AR15 that does not have select fire and only has safe and two shots, you must fire both rounds. Once the trigger is pulled you have to release the trigger to put into safe. This is the first version, garage version, of what later became the BFS.

The flat of the selector where the back of the trigger hits the selector in fire mode needs to be dremeled out 3/16 inch. This allows the trigger to pull further back and causes you to slow your trigger pull timing. Pulling the trigger too fast causes a hammer follow and you have to rack the charging handle and waste a round. The hammer follow does not cause a slam fire.

The trigger needs to have a channel 1/16 inch cut on each side of the trigger just forward of pin hole lug mounts, where the top flat of the trigger meets the cut out for the disconnect. Wrap a medium, or small with sheathing, paperclip around the trigger once, cut to length, so that the front tip of the disconnect rests on top of the paper clip, the paper clip being held in place by the channels on the side. This keeps the disconnect pushed back.

The disconnect needs to be dremeled starting at the pin hole and going back toward the end past the spring pocket, 0 to 1/8 inch. So, starting at the bottom of the disconnect at the pin hole, 0 inch, draw a staight line to the back crossing the spring pocket, 1/8 inch up from bottom of rear of disconnect. Then dremel the spring pocket also about 1/8 inch deeper. This allows the disconnect to be pushed back by the paperclip and the spring to still work.

To shoot normal again just remove the paperclip.

This came from an old post from the BFS creator where he said he used a dremel for his prototype.

When assembled, with the trigger pulled back, make sure you have a good contact overlap where the disconnect meets the rear trigger catch. A very small overlap is not good. If the overlap is too small, dremel out the selector pocket more, or, your paperclip is too thick.

Good luck and have a lot of ammo on hand. I got rid of it and went with a Velocity trigger. Great trigger and doesn't waste ammo.

Last edited by Liberate80; June 5, 2018 at 06:45 PM.
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Old June 5, 2018, 09:05 AM   #2
Join Date: October 18, 2017
Posts: 17
You know, I missed a very important distinction. On the market today you can buy a binary trigger from Doubletaptriggers that uses a similar method. They also shave out the flat of the selector, but they do something very dangerous, they shave down the disconnector catch. There is a possibilty that if you have a lower that the pin holes are far apart, moving the trigger and hammer further apart, then there runs the risk that the kinetic energy of the bolt slamming forward could cause the the hammer to trip. That is a scary prospect.

That is the distinction of the method I showed, it gives a greater connection between the disconnect and the hammer to eliminate the possibility of a slam fire.

Anyway, just wanted to tell why such a distinction is important. I would like to see doubletaptriggers make a disconnect from scratch with the rear cut at an angle and the front having an extra 1/16 inch added to the bottom. It would eliminate the paperclip, eliminate the the disconnect catch being altered and it would look a lot better.

If you want a recommendation, Fostech Echo. That is a great binary trigger with safety features and select fire. It costs a lot, but has all the desirable features. I went with the Velocity trigger, I like tighter groups. I was actually going to get the Echo trigger when stock came back in just because, but Maryland changed their laws, so, oh well. It's gimmicky anyway and I already moved on. Once you burned through money for ammo it loses its fun factor.

Last edited by Liberate80; June 5, 2018 at 09:33 AM.
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Old June 5, 2018, 04:23 PM   #3
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Join Date: November 13, 2006
Posts: 6,073
I'm not telling you how to live.You make your choices,I'll make mine.

No chance will I do or recommend those mods.

I'm not saying that you are incapable of managing a firearm with such a trigger.
Nearly everyone expects the first shot when the trigger is pulled.Unless the shooter is familiar with your gun,the second shot is unexpected.

There is potential for that to be a problem.

If there were to ever be an incident with that firearm,your Dremel modified trigger parts and paper clips......
I'm not a lawyer.
It would be interesting to see what a lawyer could do with those in a civil suit.
Maybe even a prosecutor.
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Old June 5, 2018, 05:13 PM   #4
Join Date: October 18, 2017
Posts: 17
I guess you missed where I said I dont have it anymore. It is a gimmick that wastes money. I just told people so they had the info. It is also a better trigger than one being sold commercially right now, as I described and named. Its just information, take ot or leave it.
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