I have a few 9mm ARs. (These are Colt/UZI pattern ARs and not Glock mag guns.) I have found many aftermarket AR triggers do not function in 9mm ARs. Some examples I have tried are Geissele 3gun triggers (S3G and SD3G). This applies to ramped and unramped bolts. I have found the same with CMC. Neither will pass a simple function test. Jards seem OK, but becomes unreliable in the high end of 9mm cycling rates.

I think the issue with failing to pass simple function tests is the hammers are too short and do not have a rounded head to them. Some of these triggers with some bolt combinations will completely lock the gun up and require separating the upper and lower.

These aftermarket triggers work fine in 5.56 and 300BO guns. They are light, fun, and fast. Those triggers are lighter than what I can put together for my 9mm AR. But, my 9mm ARs can absolutely smoke them in rate of fire. (Yes, I do understand why.) I just want the best possible trigger in my 9mm ARs to maximize performance.

So far, the best set up I have found is an unnotched DPMS trigger, polished, installed with JP reduced weight springs, and reducing take up with a set screw. The pull weight will come in at 3.5# to 4.0# depending on gauge placement. I have not found any trigger that runs better/faster than this... reliably. This combination is fast and works with either type of bolt. However, I would image someone out there surely has a great trigger for the 9mm AR platform that will beat what I can put together.

I want a FCG that is :
Stone Cold reliable, from function test to running anywhere between 600-900RPM
Light in pull/weight
Short on take up and reset
Moderate price range, below a limit of $350

AND, it has to beat the DPMS style mentioned above... hands down.

Note : This will be cross posted in the AR Rimfire and Pistol Calibers forum/section.

it all depends on the gun. what lower are you using?  the dedicated 9mm lowers seem to be less problematic than the mag block guns.

For reliability with a decent trigger pull, I use JP adjustable trigger and stock Colt 9mm hammer. NEVER had a trigger failure in thousands of rounds.

Colt and Rock River.  Dedicated.

I run a Geissele B-GRF with a 3.2lb spring and a Colt unramped bolt.  Never had an issue and it's very fast.  The geometry on that particular hammer seems to work.

https://www.ar15.com/archive/topic.html?b=3&f=15&t=668502

That trigger is supposedly a copy of the S3G trigger, which does not work with either ramped or unramped bolts, as noted above.   So, I would not trust it.

I see that thread just died out.

By work, I don't mean "seem to function fine".   They can be shot.   I know that.  They fail a function test.

Not with my receiver, my bolt and my trigger.  Runs perfectly.  Not a special receiver, just a Rock River that came as a 9mm.  

9mm can be finicky.  I swapped the bolt to a Colt, the mag block to a Hahn top install and only run metal form or colt mags.  Slick as snot.  

One of my 9mm ARs is a RRA.    Have you done a military function test the gun in question?  Every S3G type trigger I have fails those test in my 9mms, whether dedicated Colt or RRA, even though some seem to function/fire.

That B-GRF trigger is supposedly a copy of a S3G trigger.   Does match the same profile?

I run a Slide Fire on it so I'm not too concerned about a function test.  It's never locked or broken a hammer pin.  I don't know the difference between a function test and a military function test by the way.  I've never exactly examined the profile differences between the different Geissele triggers except for noticing many are slightly different.  I went with the Brownell's because of multiple threads that claimed they worked.  Mine does, that's all I know.

Poor Man's MP5-SD

I have 3 slide fires.    Currently, only one is mounted and it is on a 5.56/300BO spare lower for swapping around.

One of my 9mm ARs is a 7" with a SilencerCo Octane 45 HD with 9mm end cap on a 3lug system.   On it is mounted a Trijicon Reflex ACOG.  

So, I can relate.