After jt grip solutions went tits up i installed a redstar arms adjustable fcg in a blaster  grade  krink sbr... with just a smidge of tweaking it now fires on pull and release reliably.only down side is it ONLY fires on pull and release and eats ammo like candy
Upside.... its  a flame shooting monster...and  and serious fun

John

What was the "tweaking" exactly?

To get  the hammer to drop on release i adjust the over travel and the take up ... and adjust sear so it would not just follow the carrier in to battery  to little sear engagement would either ride the bolt...or...the sear would carch the hammer but when the bolt went in to battery the impact would make the sear release and fire before i released the trigger.... playing with takeup,over travel and sear position thru trial and error i  was able to get  the sear to have a solid hold on thd hammer till i released the trigger....  it has very little take up but a lot more over travel , making the sear tension "heavier" so it had more hold on the hammer  ..... holdi g the trigger with  hammer back i  let carrier  slam forward several times  then i hit the stock on my bench  several times   VERY hard....  the hammer dropped only when i released tje trigger.
**** Disclaimer*****
Playing with fcg like this can be dangerous.  Do so at your own risk!!!!!

JOHN

You're playing with fire.

National Firearms Act Definitions:

Machinegun-
Any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot without manual reloading, by a single function of the trigger.

I am not a lawyer, just a brother trying to look out for a brother.

Matt

Binary triggers are good to go. Pull is one action, release is another





Example





 

Good to know.

Matt

blu.. i will never fault someone trying to keep me outta trouble  : )......   this "mod" is legal for anyone to do but any mods to a firearm can be dangerous so please be careful.....im a wecsog "er" for almost 37 years and had  1 grandfather who was a gunsmith and another who was a watch smith... means i can mess a gun up in any timezone...

This adjustment doesn't have a secondary disconnector so the ATF may consider it a machinegun.  It's retarded, but that appears to be the position the ATF has taken in their letters to Fostech/Hawbaker and Franklin.