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 Pistol forum/section.

When looking online i have heard great things about the POF basic trigger.

With a pull weight of 4.0# to 4.5#, I don't think so.   It has to be 3.5# or less.  

JP yellow spring set.  3.5# trigger with the FCG parts you already have and trust.  Costs $10.

http://www.midwayusa.com/product/579878/jp-enterprises-trigger-spring-kit-ar-15-3-1-2-lb-reduced-power

Yes.   That is what I posted I am running.    

POF makes a 3 or 3.5lb as well  but I've never used it. I have used Molon Labe's Velocity trigger, I have used it with a slide fire stock since I don't have FA guns just SA so it would be lower end ROF I have tried, works great. Also I run in my new build a Tac con 3MR trigger & slide fire stock, not sure of ROF but is extremely fast with both together. Also I have used RRA Varmint trigger, it's 2 stage but 3-3.5lbs. Don't know if this helps you since again mine are not FA but the triggers do reset, never had any issues yet.

These are semi auto Colt and Rock River dedicated 9mm guns without bump stocks.  

I have tried a Tac-Con in them.   It was laughable.   It cost a bit more than anything else but could not touch the rate of fire compared to what I can do with a polished hammer and trigger, JP 3.5# springs, and a set screw.  

Franklin Armory Binary vaporware is what we want.

i dont think that trigger is going to be released anytime this year or next year.

Well, I am running an ALG ACT trigger right now...i was planning to put in a JP ARmageddon Roller Trigger (or a CMC but after reading this, not anymore)

now i am wondering if the JP will work....

**I have a CMMG MK9 dedicated lower and an Xproducts Outlaw upper**

I'm waiting on a Form 1 to come back and after reading a couple of threads here, I ordered a Geissele SSA today. It looks and sounds like any trigger with a full or almost full profile hammer will work.

I'll be using the SSA in a CMMG lower with a CMMG complete upper that I'm swapping to a TROS 5.5" 3-lug barrel and topping it off with an Octane 9.

If it doesn't work, I'll swap the SSA into one of my LWRC SBR's.

I use the Geisselle Rapid Fire trigger in mine (I think it's a Brownells exclusive).  Works great, but very prone to bump firing in certain hands.  I've only had it bump fire on me once, but my wife and brother-in-law almost can't pull the trigger with bump firing it.

I can't decide if that's awesome or not awesome.  Since it's a range toy 99% of the time, and doesn't bump when I shoot it, I think it's mostly awesome.

In which 9mm AR do you use that trigger?     What type of bolt do you use with it?    I would like to here more details of the gun.

This is very important.   That trigger is a copy of the S3G, which generally will not work.   Have them.   They don't work, as other have pointed out.

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

I have the ALG / QMS in all 4 9mm platforms

This is a great answer.  

OP, why MUST your trigger be under 4 pounds?  Because there's a difference between true pull weight and "heavy feeling" triggers.  Much of the heavy feel in most triggers comes not from the true pull weight, but from poorly lubricated pins and parts that just haven't broken in together yet.

Stock trigger parts aren't polished or even smoothed very much before finishing, so the hammer-to-trigger interface is rough (not in the engagement surfaces, but in the secondary contacts, like below the trigger's sear point - and even how the disconnector moves in the trigger).  This tends to smooth out after hundreds or thousands of cycles by having those surfaces rub on each other.  A lot of people do "trigger jobs" on stock parts to smooth them, but they risk going through the case hardening of the sear surfaces and making the parts likely to fail quickly.

ALG's triggers, both the QMS and ACT, start out with parts that are smoothed without damaging heat treatment.  All the accessory friction and grit are prevented before the parts are finished.  They also get improvements in the ACT by using a nickel-boron coating, which increases lubricity and wear resistance.

A stock trigger CAN be made to feel lighter by just cleaning all of the manufacturer's protective coating off of the parts and thoroughly lubricating them before installation, and then ensuring the pin bores of both hammer and trigger are lubed well as the pins are installed.  Geissele and ALG recommend a light grease on the pins; while I usually don't go with grease in an AR's lower, we're talking about a tiny bit in a very controlled space.  I can say from experience that this makes a big difference even with extremely generic parts.  It will NOT lower the pull weight, but the "feel" will be much lighter and less like you're overcoming something more than the sear surfaces' interaction.

Above all, for the same reason I want a dozen ARs.   Beyond that, the triggers help me shoot fast.   I enjoy that at times.  No lecture required.

I'm using a QC10 Colt-style lower with a JP 9mm EnhancedBolt.  Shoots like a dream for me, bump fires for others.  Go figure.

Oh, now that is different.    It is neither a standard unramped nor standard ramped bolt.  

I would love to see a good pic of the underside of that bolt.    I could not find any through  a google search for "JP 9mm EnhancedBolt", of the underside specifically.

No lecture intended, really.  It's amazing how many people decide they're going to build their rifle and don't bother learning little bits like what I posted.  A cheap, quick and easy way to reduce pull problems that is both nondestructive and effective is a boon for just about everyone, and it's worth a shot just to see if it helps with any particular trigger.

"Because you want that" is a great answer, though some people have more pragmatic reasons.  If you'd had issues with trigger pull because of arthritis or damage to your dominant hand, or just had crappy experiences with crappy triggers, my (lengthy, I know) post might have been useful, so it was worth my posting.

I will point out for anyone reading this thread that GI triggers must have a minimum pull of 5.5#.  This is a safety issue in a rifle that's going to be carried around a battlefield with the soldier having to jump, dodge, hide, run and otherwise move violently and unpredictably.  An extremely light trigger is a negligent discharge event waiting to happen.  (There, I said it.)

You have to have a ramped bolt to use the ALG or QMS triggers.  If you have an unramped bolt, then you have to use a 9mm hammer or one that has a geometry that won't break hammer pins or get jammed against the underneath of the bolt that will lock the gun up.  

The Brownell's Geissele Rapid Fire, B-GRF, seems to be the one that can work with unramped bolts.

The 3Gunners and Slide Fire folk don't care about combat.  They just want to shoot as fast as possible.  It's just one aspect of shooting which people enjoy.  It's not a self-defense or combat thing at all.

When and if select fire becomes affordable, these conversations will not take place.  Until then, folks that want to shoot fast will find a way regardless.

You are right.   Those are good points... for other people.   Those points are a bit basic for me.  I have a gun for everything, short of a $25K shotgun.  LOL!  I'd buy a M16 instead.   That is just me.   But, seriously.   You are certainly right about NDs.   We are both probably retired.   I'm a combat medic, double branched engineer and light infantry officer, and recon team lead.   So, I know people do vary in every imaginable way.    Also, not every military weapon gets the attention many of us here put into our weapons.  

Bottonline: I get it.   Hope you understand.   I think you do.

You are right about shooting fast.

Well, the B-GRF must be somehow different than a S3G, and it is supposed to be a cheaper copy.    I know a S3G and SD3G will both hang up on a notched, unramped bolt.    Both of those triggers also tend to demonstrate hammer follow during a standard military function when used with several common ramped bolts.

JP 9mm Enhanced bolts might also be another exception to through into consideration, but I have not verified the design/construction.

I'll try to remember to send you one but no promises.  I'd call the folks at JP, they've been very helpful in my experience.

Have a SD3G in a suppressed SBR with no issues, ADCO glock cut/ unramped bolt.  It would not function with the bolt ramped.

Thanks for adding to this thread.    The issue with unramped bolts and some hammers is they can jam or lock up.   There is a notch on the underside of many to most unramped 9mm bolts.   That thin little notch, which would be removed with the slightest ramping,  hangs up on some triggers.

Would love to know more regarding the underside of your bolt.  

When running JP yellow Springs I mill the tail off the hammer to increase hammer velocity to minimize light strikes and have never had a problem and with ACT trigger and hammer I get a 4lb pull every time and with the set screw I get a very nice crisp break.

My cheapo set up as well...
However, the X39's get increased power hammer springs.
I use a surface grinder to dress the tail after I use a cutoff wheel to chop it.

I run an SSA-E in my 9mm Build w/ JP Bolt Carrier.  No problems at all.

I'm running a CMC 3.5# flat trigger in my 9mm AR. Glock frame, with a Mas Defense bolt, ramped and glock cut, with a 4.5" barrel. Nothing but success with my setup

+1 for ALG ACT with the yellow springs if you don't get a new one with purple springs

i'd be interested in that two shot trigger, the one that is pending atf approval.  brings a 9mm AR close to what is should be.

ETA: Franklin armory.  there is a 10 pg thread about it

Geissele SSA.

Running a KAC trigger I pulled from another rifle

I have a spikes 9AR. Upper and lower. I used the factory trigger with JP springs and the magic set screw.
Still has a bit more creep than I'd like. The safety interferes with the trigger so I have to back the screw off just a tad and that creates the creep. I think its possible to tweak the safety a bit.
I'll look into it the next time I strip the lower down for a major cleaning/grease job.

No one has mentioned RRA Varmint 3lb trigger, has anyone tried one? I want to with my colt "unramped" bolt but thought I'd ask before I swap parts out. it's hammer appears that it should work IMO.

I'm using a CMC 3.5 and no problems here either.

QC10 Glock lower, JP 9mm bolt with Glock cut, JP 9mm silent captured spring.

Sorry if this is a basic question...

Can someone post photos of ramped and unramped bolts?

I have a cmmg 9mm bolt and i think it is ramped...

Sounds like the JP bolt works with everything haha so maybe ill get the trigger i want and if it isnt good to go just swap my bolt

ALG ACT with JP yellow/red springs

Now that I've finished my build and run it through it's initial paces, I thought I would share that the Timney single stage trigger works great In my QC 10 Colt lower.  I'm also using the JP Enterprises 9mm bolt.  So far, all is good.  I know I'll get getting one of these triggers for my .223 AR.  :)

Agree!  I am running the Timney 3lb (667S) trigger with a CMMG bolt in a QC10 Colt lower.  I will also get this trigger or the 4lb version in my next AR15 build.

I have a RRA match trigger(4lb) in a 9mm colt pattern pistol with a ramped bolt.It doesn't always reset the hammer.If you then pull the charging handle it will eject the loaded round,load another round and reset the hammer.Works every time manually but not on actual firing.

I am thinking about trying the spot weld trick on the bolt ramp to help reset the hammer back.