DK Firearms

DIY Lightening and smoothing up you factory AR trigger

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  • Dawico

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    Let's face it, a standard factory AR trigger sucks. 6+ pounds and usually gritty and "different" every time you pull it. Lawyer triggers are the best way to describe them. Heavy and made more for high stress situations than precision shooting. They are the reason the aftermarket trigger market is so hot and generally expensive.

    You can spend money on an upgrade or work the factory trigger yourself.

    This is my fix using all the factory parts and springs. I have my triggers down to about 2.5 pounds and they are safe. Don't get me wrong, they still don't compare to my CMC trigger, but they are so much better than factory and the price is much better too.

    As with anything these days, you are on your own here. I make no guarantees on your outcome or the safety of your trigger.

    The problem with factory triggers is their geometry. The sear to hammer engagement is purposely designed to be heavy.

    The easiest way to see it is to seperate your upper and lower and pull the trigger. *** Do not let the hammer strike your lower. *** This will cause damage to your lower. Either use your finger or a foam ear plug to keep the hammer from striking the lower.

    If you watch the hammer movement while pulling the trigger you can see the hammer drop a little while the trigger is being moved. This means that while you are pulling against the trigger spring you are also fighting the hammer spring.

    My fix is simple and eliminates the extra pressure that the hammer spring exerts on the trigger. You need to get the trigger out of the lower to work on it. This includes taking the grip off, safety out, hammer out, and finally the trigger. It is much more simple than it sounds and I am not going to go through it. The information, if needed, is covered many times over elsewhere.

    The front end of the trigger needs to be squared up. If you put the trigger and hammer together on the outside of the lower you can see how they mesh up. The angle of the trigger sear pushes the hammer down during the pull.

    I start with a piece of sandpaper on a flat surface to square up the sear. I use 220 grit to start and higher grain paper to smooth it up. It doesn't take much but you do have to reassemble it in the lower to get a real feel for your progress. Slow and easy. Sandpaper is plenty to do the job. A Dremel or grinder is too much and not necessary.

    This is the angle of the sear from the factory.

    77c71a460d210735f5517a6a400abe22.jpg


    This is what square looks like and what I shoot for. Don't over cut the angle as that is just asking for trouble.

    42e54e06f75d8abde9ea32098e3aec1c.jpg


    As you can see, you really only need to recut the top third of the sear. That is all that makes contact with the hammer. This is my finished product with a nice 2.5 pound smooth pull.

    349b56d13b3015ab1a9b0debf33870bc.jpg


    I only have a couple hundred pulls on my recut triggers so I can't attest to their long term durability. They haven't shown any signs of excessive wear or worse yet, double firing. So far they are working well and I have recut AR15 and AR10 triggers.

    Work slow and take it easy. Test it a few times as you progress so you don't take too much off. It doesn't take much to get the pull lightened and smoothed out.
    Guns International
     

    Dawico

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    Interesting, thanks for sharing. I didn't think there was such a simple way to lower the pull weight without getting crazy careful. I assumed it was on par with cutting diamonds as to not mess up the mechanics. Lol
    That is just it. It is simple and the original mechanics are just bad.

    First time I tore one apart I could see easy improvement. It isn't a complicated mechanism with many moving parts.

    I haven't yet, but you can screw one up easily. Cutting the sear past square would do it. Working on the hammer engagement would make it unsafe too.
     

    Glockster69

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    Nice thread, thank you.

    I think my Rock River 2-stage trigger gauged out at @ 4lbs. I'm pleased with it but may tweek it a little some day.
     

    Bravodigger

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    That is just it. It is simple and the original mechanics are just bad.

    First time I tore one apart I could see easy improvement. It isn't a complicated mechanism with many moving parts.

    I haven't yet, but you can screw one up easily. Cutting the sear past square would do it. Working on the hammer engagement would make it unsafe too.

    I might give it a try on one of my stock triggers and see how it compares to my AR gold and then back against another stock trigger. If it feels right I might just have to change my ways..
     

    Dawico

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    I might give it a try on one of my stock triggers and see how it compares to my AR gold and then back against another stock trigger. If it feels right I might just have to change my ways..
    With the gun split in half watch the hammer movement while pulling the trigger. I bet your AR Gold barely (if at all) moves the hammer during the pull.
     

    Dawico

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    Nice thread, thank you.

    I think my Rock River 2-stage trigger gauged out at @ 4lbs. I'm pleased with it but may tweek it a little some day.
    Anything to help.

    The RRA trigger may be better served with a spring change but I have never done it.

    I wore my RRA 2 stage out after a few thousand rounds and it started doubling on me. I pulled it and swapped in a standard trigger. The change was very noticable and was the first factory trigger I worked on. After modifying it I never bothered with sending the RRA trigger in.

    Maybe I will dig that trigger out and see if I can straighten it out. I assume it is a little different design than a stock trigger though. If I have any luck I will report back.
     

    Dawico

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    I just checked my CMC trigger and there is absolutely no hammer movement during the trigger pull. Besides being all fancy with light weight parts and springs the geometry of the trigger parts appears to be the same as stock. It would seem that a square cut sear is the basis for a good trigger.
     

    Vaquero

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    I just finished reassembly and testing.
    Holy crap!
    Just awesome!
    Maybe a touch too close to release if the safety is on, but no hammer drop in spite of rough treatment.
    Smooth and many pounds lighter pull.
    Squeeze the trigger with the safety on and all creep is taken up.
    Flip the safety and a very slight trigger movement releases the sear.

    I can't wait to hit the range.
    Thanks Dawico!
     

    Bozz10mm

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    I've got a spare trigger that came out of my Bushmaster when I replaced it with an ALG Defense QMS. I just might try that and install it in the PSA AR. I've got some 200 grit, but I need to get some 1000 grit for final passes. I don't think I want 2.5 lb pull, but 4.5 or 5 lbs would be nice. The Bushy is at 6.5 lbs now. PSA is 6 lbs.
     
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    Dawico

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    I've got a spare trigger that came out of my Bushmaster when I replaced it with an ALG Defense QMS. I just might try that and install it in the PSA AR. I've got some 200 grit, but I need to get some 1000 grit for final passes. I don't think I want 2.5 lb pull, but 4.5 or 5 lbs would be nice. The Bushy is at 6.5 lbs now. PSA is 6 lbs.
    The 200 grit will do fine. Anything more is just bringing it to where it will be after a little use and it smoothes itself up. I mainly hit them with more grit because I have the sandpaper laying around anyways.
     

    TacticalPandaBear

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    I wouldn't recommend sanding down your trigger sear this much, you are going past the case hardening to where the metal is softer. The trigger pull weight and angle of the trigger sear with the hammer sear are there for safety. Altering the angle greatly reduces the safety of the trigger design.

    All you really need to do is polish the sear surfaces with some metal polish. Don't over do it. The trigger pull will at least be smoother and the break cleaner.

    If you want a better trigger, spend the money on a trigger designed to function safely while being lighter and having a clean break.
     
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    Dawico

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    I wouldn't recommend sanding down your trigger sear this much, you are going past the case hardening to where the metal is softer. The trigger pull weight and angle of the trigger sear with the hammer sear are there for safety. Altering the angle greatly reduces the safety of the trigger design.

    All you really need to do is polish the sear surfaces with some metal polish. Don't over do it. The trigger pull will at least be smoother and the break cleaner.

    If you want a better trigger, spend the money on a trigger designed to function safely while being lighter and having a clean break.
    Of course this is a proceed at your own risk operation.

    After having to work with hardened steel, I would be surprised if any of the triggers I have worked on are hardened. Mine are all cheap parts kit type triggers. I could be wrong though but they are pretty easy to work on if they are hardened steel.
     

    hoghunting

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    After having to work with hardened steel, I would be surprised if any of the triggers I have worked on are hardened

    The AR triggers and hammers are only surface hardened - most after market parts are different - after you break the surface, the metal is not hardened.
     
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