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Thread: AR trigger job night

  1. #1
    Senior Member kyratshooter's Avatar
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    Default AR trigger job night

    For two days I have been an AR mechanic to the point of changing every optic on every AR platform I own and switching around buffer tubes, swapping barrels and generally making a mess of all my previously carefully zeroed toys. I now need to zero everything I own.

    Based on the weather forecast tomorrow would be a good day but I have one more thing to attempt to ruin before heading to the range.

    While one of my AR platforms has a very good out of the box trigger I checked the pull on the one which I decided to rebuild for accuracy ad discovered that what I though was about a 6 pound trigger was actually an 8.5 pound pull and rifle #2 was not much better at 7 pounds.

    Both are Anderson Receivers with PSA build kits. I have decided to polish the triggers tonight before I head to the range tomorrow.

    My goal is a smooth and safe 4 pound trigger, which is the minimum for NRA competition and I want to be able to use either receiver with either upper so I will always have a spare unit when shooting CMP at the local clubs.

    So my goal is to reduce the trigger pulls on these two lowers by 1/2.

    I am not planning to use one of the reduced power spring kits, primarily because I use a lot of Russian surplus ammo in these guns and that stuff is notorious for having hard primers. I want to retain full hammer pressure. My past experience with reduced power spring kits has not been enjoyable and I avoid them when possible.

    And I have absolutely zero interest in "drop in" triggers that cost more than my base rifles. Only time I ever did that was using a Timney trigger in a Mauser custom rifle once back in the '70s. ($100 trigger and $300 work and parts on a $50 rifle! Yep I was insane.)

    So tonight has been designated as trigger polishing night here at the shack. All beer has been removed and all the Evan Williams is put away safely, only to be recovered after all goals have been met. I even stopped drinking coffee at noon to eliminate caffeine shakes while working on those infernal tiny hammer notches.

    I also found the extra powerful reading glasses and the big Sherlock Holmes magnifying glass to check the progress.

    So wish the old geezer luck and I will report the results latter, or even as the work progresses.

    Yes I live a dull and boring life, it keeps my blood pressure in check and reduces the intake of antacids.
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  2. #2
    Senior Member hunter63's Avatar
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    An evening in the shop is still an enjoyable endeavor (when thing go well...LOL)......DW calls it "putzin'.....
    So be it....
    Good luck ....keep us posted.
    Geezer Squad....Charter Member #1
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    Administrator Rick's Avatar
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    Would it bother you if..oh, say...a half dozen of us watched over your shoulder?

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    Super Moderator crashdive123's Avatar
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    I spend most evenings in my shop working on knives. Yeah, I know.........I have no life.
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  5. #5
    Senior Member kyratshooter's Avatar
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    Quote Originally Posted by Rick View Post
    Would it bother you if..oh, say...a half dozen of us watched over your shoulder?
    I am doing almost exactly what this guy is doing.

    http://www.shtfblog.com/diy-ar-15-tr...job-for-17-06/

    Difference is that I am using a set of India stones and buffing with a cratex wheel in a Dremil tool.

    I have got one of the brood finished and it reminded me of several points of reference.

    The most important is that the AR has two trigger pulls. One when you rack the charging handle back and another when the rifle cycles and the trigger "resets". The "reset" pull is lighter than the pull when you rack the charging handle.

    The one I have just finished has a "reset" pull of 5 pounds but if you rack the charging handle the pull is 7 pounds. It is now smooth and crisp, but it is still 7 pounds for the first shot.

    This seems to be about the best I can get without changing the angles on the contact points or messing with the springs. The trigger spring alone has a 1 1/2 pound pull, which seems excessive since I have a couple of rifles with 2 pound pulls.

    I may change out the trigger springs, since they do nothing during cycling but raise the trigger to catch the sear notch of the hammer on reset and it would be an easy and cheap 1 pound adjustment.
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  6. #6
    Senior Member Desert Rat!'s Avatar
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    Sounds like a good time to me, drinking beer and messin with guns

  7. #7
    Senior Member hunter63's Avatar
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    Quote Originally Posted by Desert Rat! View Post
    Sounds like a good time to me, drinking beer and messin with guns
    Yup...Just not while you are shooting them.......
    Something about Genuine Draft and Hopps #9 when cleaning at the bench.
    Geezer Squad....Charter Member #1
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  8. #8
    Senior Member kyratshooter's Avatar
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    Well here we are one month past the last post and I have spent much of this tie on a quest, the search for the magic AR trigger.

    In the past month I have done things to AR springs, triggers and hammers which have bordered on the insane. Not all of it worked but some of it did so I am back to report the progress and give recommendations whether you want them or not.

    First of all I have learned that an AR trigger is a force to be reckoned with. It was built to withstand the NATO drop test of the 1960 era which happened to be a free fall from two stories onto a concrete slab. That specification resulted in a very secure trigger that broke at 8-12 pounds on the issue rifle.

    I had 4 platforms when I began this escapade and three of them broke at 8 pounds and one broke at 6.

    The method that Stoner used to make such a secure trigger was the use of extremely strong springs in the fire control group. The springs were so strong that huge parts could be used as the hammer and trigger to endure the abuses of full auto fire, or one might say the shock of stopping full auto fire.

    The result, in a semi-auto AR rifle is that the parts and springs are way more robust than necessary and still have the ability to pass that NATO drop test without releasing. Now if you have a stock trigger and you feel that your trigger is fine believe me, it is not fine. You just do not know that it is atrocious.

    It is sort of the same thing as being used to ugly women just because that is all that is around. When you see a pretty one you are going to know the difference!

    After a good polishing of the mating sear and hammer surfaces did not contribute to much improvement in trigger pull. One can only do a certain amount to surface hardened parts before damage to the part results. I decided to investigate the actual source of the hard trigger, which was the springs.

    Beginning this phase I acquired a new lower build kit which provided me with a new hammer and trigger as well as new springs all through so that if I damaged any of the components during my experiments I would have mil-spec replacements. None of the individual parts in the FCG cost more than $15 and the whole kit totals about $40 from PSA.

    Realizing that the most improvement would come from reducing the force of the hammer spring I preformed two acts of violence on the hammer and spring. The needed force of a hammer is the age old equation of weight x speed so I decided to reduce the weight of the hammer so that a lighter spring would provide the same striking force.

    I bobbed the AR hammer, removing almost 1/3 of its mass. I did this by removing the hook at the back of the hammer that has zero function in a semi-auto AR.

    With the standard spring this reduced lock time beyond belief! Probably cut it by half.

    Not needing all that force to punch the primer I then cut one leg off the hammer spring.

    The most amazing thing about cutting half the force from the hammer spring was that not only did it reduce the trigger pull to almost nothing, at half power it was still popping the primers on the notoriously difficult to ignite Wolf steel case ammo. The AR hammer spring is almost twice as powerful as it needs to be.

    The problem was that sometimes it didn't pop the primers. About one out of ten did not fire. That is unacceptable.

    Do not cut one leg off your hammer spring. It don't work right when you do that.

    This was about the time I was going through the Midway website on the computer and found the products of JP enterprises. They furnish a wide range of trigger parts and assorted springs to obtain all different weights of pull when combined with other components.

    They are also cheap. $10-$14 for a set of hammer/trigger/disconnector springs matched to proper weight so that they will function properly in the FCG and pop any primer they encounter.

    http://www.midwayusa.com/s?userSearc...temsPerPage=48

    Having 3 platforms to modify I ordered two sets of red/yellow springs and one set of "mellow yellow" springs. The sets are color coded. Red hammer springs are stronger than the yellow hammer springs.

    The yellow trigger springs have about 1/2 the force of stock trigger return springs. That is not a problem since all the trigger spring needs is enough force to reset the disconnector. The stock trigger spring alone is 1 1/2 pounds pull.

    When I installed the two yellow springs in the lower with the polished H/T and bobbed hammer I had an instant 2 pound pull that still functioned 100%.

    It is the kind of trigger that makes you mad because they don't come like that from the factory. They could do it if they wanted too.

    On action #2 I did almost everything differently. This is the rifle I have built as a utility gun which is within the specs of the CMP program, which specifies a minimum 4 pound trigger.

    On this lower I used the "enhanced trigger group" offered by PSA. This offering consists of a mil spec hammer and trigger that are nickel plated and polished. I did not modify the parts in any way. I installed them using the red hammer spring and yellow trigger spring from JP. This combination gave an instant 4 1/2 pound trigger pull that is so slick and breaks so crisp it is a joy to shoot.

    http://palmettostatearmory.com/psa-a...d-trigger.html


    This combination is the best deal around.
    That is especially true for the person that is not adept with use of an angle grinder on precision parts and the patience to hand polish what is left over. The PSA enhanced group is around $45 and the JP springs are $11. The parts and springs can be installed by anyone that knows how to punch the pins out of the lower and replace the hammer and trigger with the new springs installed. There is no experimentation to do or modifications to preform. The parts work and do what is expected of them.

    $50 and the trigger pull is cut in half and retains 100% reliability.

    It is a really good deal for the guy that does not want to spend $200-$300 for an aftermarket drop in unit but still wants an acceptable trigger that is good enough for work out to 600M.
    Last edited by kyratshooter; 03-18-2017 at 12:31 PM.
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  9. #9

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    [QUOTE

    so does this PSA kit get rid of the overtravel? thanks

  10. #10
    Senior Member kyratshooter's Avatar
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    Quote Originally Posted by incide View Post
    [QUOTE

    so does this PSA kit get rid of the overtravel? thanks
    The PSA nickel plated trigger has slightly less over travel than the stock trigger. I noticed that as soon as I assembled the parts. It does still allow the safety to operate freely, which is often a problem when trying to overcome trigger travel.

    I am usually sensitive to over travel but with the AR platform as soon as the trigger releases all he!! breaks lose, the bullet is gone and I do not think about it too much as the round fires, the bolt goes crazy and the buffer tube echoes like a freight train going through a plastic tunnel 1/8" from my ear.

    The only time I notice over travel in the AR is when I am dry firing or specifically working on trigger function. It is like recoil when hunting, you notice it at the target bench but never think about it when shooting at game.
    If you didn't bring jerky what did I just eat?

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