I installed this 'binary trigger' over the weekend and just put my first 100 rounds or so through it.
A binary trigger is one that can fire both on the trigger press, and on the release, resulting in two shots being fired in the time it normally takes to fire one.
Two companies make these types of triggers for ARs (that I know of), Fostech and Franklin. This review only covers the Franklin product.
https://www.franklinarmory.com/products/binary-firing-system-gen-iii-trigger-pack
https://fostechoutdoors.com/shop/index.php?l=product_list&c=15
Cost and availability - Both of these triggers are pretty expensive, with the Franklin Armory part running $390 and the Fostech part being $479 (MSRP).
I was able to find the Franklin part for about $360 online, but was not able to find the Fostech trigger anyplace except GunBroker. The Fostech is in very, very short supply, and unless you are willing to pay about $100 over retail on the auction sites, you simply won't be able to buy it right now.
Components - The Franklin BFS-III kit comes with the trigger parts, extra hammer and trigger springs, and a buffer spring, along with instructions, a Safe/Semi/Binary decal for the rifle, and a small, sample tube of SLP-2000 EWL grease (good stuff BTW).
Installation - The installation is no different than most AR triggers. You remove the old safety, hammer and trigger and install the new BFS-III parts. They do include lighter-weight springs if you want to use them, but for reliability I stuck with the plain (clear) Mil Spec springs.
You also have to remove your existing buffer and spring, and reinstall the buffer using their (included) heavier-rate spring. This helps mitigate 'hammer follow' which made the first generation of this trigger very unreliable. The manual also warns you that you may need to increase your buffer weight (not included) if you see hammer-follow even with the heavier spring.
Use - I only shot about 100 rounds through the gun today, but it functioned *almost* flawlessly.
Just like a SlideFire stock, it takes a little bit to get the hang of shooting long bursts with it. You have to get your trigger finger in a rhythm that will go fast in a controllable manner. A couple of mags should get you going, and the rate is very comparable to full-auto.
In Semi mode it's exactly like every mil-spec trigger AR you've ever shot. And Safe is just... 'safe'.
If you are in 'binary' and have pressed, but not released the trigger, you can flip the selector to 'semi' and it will not fire the gun when you release the trigger. And like most AR triggers you cannot put the gun into safe unless the hammer is cocked.
The only problem I had with it was (2) light primer strikes, both of which happened during longer bursts. I don't know if this was due to 'hammer follow' but it only happened with this trigger installed and both rounds shot fine when reloaded and run through the gun again.
I may find that I will have to go to a heavier buffer to slow the cyclic rate even more if I want to keep this configuration (and I do). The good news is that requires no real 'installation' and I can try different buffers right at the range to see which one works best with this setup.
Overall this seems to be an effective, if somewhat expensive way to simulate full-auto fire. Although compared to the cost for a SlideFire stock it's pretty similar, and compared to a real select-fire gun... it's dirt cheap.
A binary trigger is one that can fire both on the trigger press, and on the release, resulting in two shots being fired in the time it normally takes to fire one.
Two companies make these types of triggers for ARs (that I know of), Fostech and Franklin. This review only covers the Franklin product.
https://www.franklinarmory.com/products/binary-firing-system-gen-iii-trigger-pack
https://fostechoutdoors.com/shop/index.php?l=product_list&c=15
Cost and availability - Both of these triggers are pretty expensive, with the Franklin Armory part running $390 and the Fostech part being $479 (MSRP).
I was able to find the Franklin part for about $360 online, but was not able to find the Fostech trigger anyplace except GunBroker. The Fostech is in very, very short supply, and unless you are willing to pay about $100 over retail on the auction sites, you simply won't be able to buy it right now.
Components - The Franklin BFS-III kit comes with the trigger parts, extra hammer and trigger springs, and a buffer spring, along with instructions, a Safe/Semi/Binary decal for the rifle, and a small, sample tube of SLP-2000 EWL grease (good stuff BTW).
Installation - The installation is no different than most AR triggers. You remove the old safety, hammer and trigger and install the new BFS-III parts. They do include lighter-weight springs if you want to use them, but for reliability I stuck with the plain (clear) Mil Spec springs.
You also have to remove your existing buffer and spring, and reinstall the buffer using their (included) heavier-rate spring. This helps mitigate 'hammer follow' which made the first generation of this trigger very unreliable. The manual also warns you that you may need to increase your buffer weight (not included) if you see hammer-follow even with the heavier spring.
Use - I only shot about 100 rounds through the gun today, but it functioned *almost* flawlessly.
Just like a SlideFire stock, it takes a little bit to get the hang of shooting long bursts with it. You have to get your trigger finger in a rhythm that will go fast in a controllable manner. A couple of mags should get you going, and the rate is very comparable to full-auto.
In Semi mode it's exactly like every mil-spec trigger AR you've ever shot. And Safe is just... 'safe'.
If you are in 'binary' and have pressed, but not released the trigger, you can flip the selector to 'semi' and it will not fire the gun when you release the trigger. And like most AR triggers you cannot put the gun into safe unless the hammer is cocked.
The only problem I had with it was (2) light primer strikes, both of which happened during longer bursts. I don't know if this was due to 'hammer follow' but it only happened with this trigger installed and both rounds shot fine when reloaded and run through the gun again.
I may find that I will have to go to a heavier buffer to slow the cyclic rate even more if I want to keep this configuration (and I do). The good news is that requires no real 'installation' and I can try different buffers right at the range to see which one works best with this setup.
Overall this seems to be an effective, if somewhat expensive way to simulate full-auto fire. Although compared to the cost for a SlideFire stock it's pretty similar, and compared to a real select-fire gun... it's dirt cheap.