Gunsmithing Trigger job on an AR15

Greg Jacobs

Private
Minuteman
Aug 4, 2010
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0
69
Oregon
I have a question for you folks out there. I’m replacing the trigger and fire control group in an ol’ Colt Commander and I received my parts the other day. Noticing that the casting is kinda rough,(Mil spec trigger) I polished the contact surfaces of the sear and the trigger. My question is should I polish the contact surfaces on the disconnector and the hammer? They to are rough and I though it may smooth out the trigger upon release, as that’s when the disconnector resets the trigger. My concern is can I expose myself to the possibility of doubles just by polishing it?? Any help and comments about the benefits of polishing those surfaces would be appreciated….Thanks!
 
Re: Trigger job on an AR15

I've done the sear, trigger and hammer many times with out issue. Just try to keep everything flat and don't over do it. Then there is the trick of running a 1/4x28 set screw up the pistol grip screw hole to help reduce the creep.
 
Re: Trigger job on an AR15

Thanks for the tips. I installed the trigger group first to see what I was starting out with. It was 6lbs and gritty with a rather long pull. I polished the surfaces and reinstalled. I used a lighter hammer spring and with that the pull was smooth and down to 4lbs. But still a long pull. I then did your trick with the set screw; It dropped to a 4lbs crisp! Thanks for the tip.
 
Re: Trigger job on an AR15

19 I measured the length in my ar and determined that a 3/8" long 1/4 28 setscrew would fit with my grip screw. I took the pistol grip off, the hammer, trigger and selector. I ran the setscrew up so it was a few threads down and put some loctite on the threads. Then I reasembled the trigger and selector and screwed the set screw up until it pushed the trigger up to the selector with it in the safe position and backed off until the selector worked smoothly. Reassembled the hammer and grip. If there is any interference between the grip screw and setscrew then shorten the grip screw. Test your trigger and safety for proper operation and you should be GTG. I almost forgot to mention i spent about $.20 for thr setscrew.
 
Re: Trigger job on an AR15

be careful folks. polishing is one thing. grinding metal is another...

there are enough half ass AR fire control groups out there it is becoming hard to tell if they are actually "mil spec" or not... the term "mil spec" can be confusing in and of itself... regardless, the majority of these triggers are surface hardened rather than through hardened. should you grind past that hardening the metal below is softer, essentially, and wears quickly by comparison.

at our last CCA rifle course the pics below represent a brand new bill springfield trigger job. it failed on magazine four.

i'm not hacking on bill. while i've contacted him several times about adding his work to my AR15 fire control group evaluation and comparison article, he has never responded. in my opinion these types of 'quick - down and dirty' trigger jobs are for the plinker only. should you own a weapon that requires reliability and durability, i'd reconsider.

again, some polish isn't a bad thing, but in most cases you may not gain a lot. just go slow and be careful. the worst part about this is the geometry... you're probably camming the hammer up with nearly every 'mil spec' trigger, so you really can't do a good job without removing a lot of material. then the real rub comes with the sear breaking... take a look at that rounded edge along the pics... not good. that is the last thing you'd wish for.

without a jig and something very rigid it is darn tough to hold the right angle and not slip over that edge, thus rounding it. you also probably won't hold it uniform along the entire surface, thus creating low spots and high spots. run some prussian blue across one of these when you're done, use it once, yank it out and inspect it under glass. you'll shit yourself...

please don't misunderstand. i'm not advocating you not doing some work yourself, but triggers/fire control groups are a big deal, so be careful and always give them the consideration they deserve.

hope the pics and thoughts help. best of luck.

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Re: Trigger job on an AR15

In my garage I can get a 12 pound military Mauser trigger down to ~2 pounds and have it work reliably.
In my garage I can get semi auto triggers with disconnectors down to ~ 4 pounds before they start doubling [machine gunning].

I can buy an aftermarket bolt action trigger that is 2 ounces.
I can buy and aftermarket semi auto trigger than is 2 pounds.

15 year ago I bought Sav110 30-06 used for $75 and an aftermarket JP AR trigger for $100.

I took the stock off the Sav110 and adjusted the trigger in 5 minutes.
I installed the JP trigger over an 8 hour frustrating experience.

The Savage trigger is much nicer and more adjustable.