BFS 3 BINARY TRIGGER GOES RUNAWAY ON 9MM CARBINE

[bellavite1]

Hello guys.
I have a Franklin Armory BFS3 binary trigger, which has so far worked great on my AR pistol.
Because of ammo cost I decided to move it to a 9mm platform.
Just today I installed it on a Freedom Ordnance FX-9 9mm Carbine.
https://freedomordnance.com/fx-9-9mm-carbine/



When testing the safety, I discover that the BFS3 selector allowed just enough movement in the trigger for the hammer to drop.
Worse than that, pulling the trigger with the safety on on a live round resulted in my firearm going full auto in full runaway mode before stopping with the hammer dropped onto a live round that exhibited a light strike.
This happened consistently on both tests I ran.
It worked great in semi auto mode (Disconnector catching the hammer, one round at a time), It worked amazingly in Binary mode (!!!), but 10 years in jail are not something I look forward to, so I removed the trigger and re-installed the factory one.
The hammer provided with the weapon has actually extra sear engagement than a standard AR Hammer.

Supposedly the dimensions in the lower are standard AR, so much that it accepts all kind of AR parts, so, what gives?
Why does this happen only with the safety on (no runaway issue with the selector on semi or binary, works exactly as intended)?


HELP!

[The Rat]

Did you contact Franklin Armory about it?

[Great-Kazoo]

Did you contact Franklin Armory about it?

Sounds like the trigger is not resetting / follow thru.

Before calling go with the stock (heavier) Hammer & trigger springs, based on past experience with light triggers i used the stock springs. . Then switch out the buffer spring, they have 2 (the heavier of the two has a rubberish coating on one end) If you used one of their buffer springs, switch back to stock recoil unit. . BUT it may be an issue with the 9mm ramped bolt.

[bellavite1]

Sounds like the trigger is not resetting / follow thru.

Before calling go with the stock (heavier) Hammer & trigger springs, based on past experience with light triggers i used the stock springs. . Then switch out the buffer spring, they have 2 (the heavier of the two has a rubberish coating on one end) If you used one of their buffer springs, switch back to stock recoil unit. . BUT it may be an issue with the 9mm ramped bolt.

Well, THAT (and changing the 9mm hammer with a mil-spec) did it.
Thank you!

[bellavite1]

I did, waiting for a reply.
I thought I knew how a fcg works but now I am confused... ��

[kidicarus13]

I'll buy it.

[archangel]

I think I read somewhere if using the trigger on a 9mm ar it has to be modified at the factory to work properly

[Great-Kazoo]

I think I read somewhere if using the trigger on a 9mm ar it has to be modified at the factory to work properly

Not for the B3 as it's a stock looking one. It's the drop in triggers that have reset issues due to the 9mm bolt being ramped.

[roberth]

I just installed a B3 in a CMMG 9mm lower, no problems with dry fire, works just like the B3 in my 556. I need to get to the range to confirm.

[Circuits]

9mm has a different, heavier recoil impulse, because it's a blowback system, that may be encouraging it to runaway with a light trigger.

The safety engagement issue is probably tolerance stacking of different parts, but without handling the firearm and putting it through some function tests, I couldn't tell what exactly is at fault.