I just purchased first AR lower, upper and their related parts. I have a 1911 and I did the trigger Job on it with lots of patience and it made a huge improvement. I have read that others have done it with their AR. I am interested in doing mine, however I wonder about issues arising from the fact that the parts are case hardened. I don't think I would remove an material purposefully, but I would want to polish the surfaces. I was all set to go when I started reading the AR books by Sweeny when he says that doing a trigger Job will remove the hardened material making the trigger wear faster.

What do you guys think? This will be a plinking gun. Mostly milspec.

Have any of you done a trigger Job, then have the trigger wear or become unsafe over time?

Thanks!

Google ALG ACT.

You can polish the surfaces and add a JP light spring kit to help a little.  For about $115 you can get the JP kit with all the parts, install yourself, and have a nice 3lb trigger with adjustable travel and reset.

Start polishing sear surfaces and suddenly you're going to end up with a gun that doubles eventually. See above.

The Spikes Battle Trigger is similar.  Both are in the $55 range, NiB coated, and butter smooth with a touch of grease.  I own both, can't tell the diff between them.  Fine one or the other on sale and get either and avoid trouble down the road.

I've owned CMC, Wilson, Gieselle, have had trigger jobs done for me and done my own.

My advise, do it. a little polishing can clean up a mil spec trigger to be pretty descent and it's free, remember, you can always polish it a little more but you can't put material back on once you remote it, so go easy.

for a plinker, worst case is it doubles, if that happens, stop shooting it and just replace it with a ALG or whatever. I wouldn't spend the money on springs when for a few dollars more you can get a complete trigger group that is backed by a reputable company.

You can get a stock trigger lighter (JP yellow springs) and polish off some grittyness but it will never come anywhere close to an aftermarket trigger.
Downside with lighter springs is You also get lighter primer strikes. You'll never get a creep free trigger because the lighter springs will actually increase creep.

At best You get an OK trigger. It's up to You if it's worth the time.
For me it's not, an aftermarket like Geissele or Hiperfire is so much better.

Changing the trigger spring does not effect ignition reliability.  Ignition is a function of the hammer spring.

On a milspec FCG creep can be addressed by tuning the disconnector and by adding a setscrew thru the grip hold down screw.

Case hardening can be very swallow on some FTG's you can harden the sear surface with Kasenit if you alter any contact surface.

Learning to tune the FCG isn't difficult, I would recommend you buy a few used FTG's, a few good stones, and a trigger fixture and go for it  You may fubar the first one or two you do but you learn what it takes to make a milspec FCG creep free and at the pull weight you prefer.  You are going to invest time and money that could buy a aftermarket trigger.  Nothing wrong with aftermarket FCG's, for many it's a better choice.

Google Bill Springfield Trigger Jobs

Trying to polish an AR trigger is a BAD IDEA!

For the first decade of AR-15 prominence in NRA high power rifle competitions many attempts were made to polish and tune mil.spec. triggers. These attempts always ended up with triggers that wore out prematurely, usually in the middle of a tournament.

As already noted, the trigger will fire two shots (double) when they fail. One shot is fired when you squeeze the trigger, a second shot is fired when you release it. Sometimes simply replacing the hammer with a stock unmodified G.I. unit can get the rifle back up and running.

While I discourage tuning stock triggers, especially since there are so many superb AR-15 triggers available on the market nowadays, if you insist on tuning leave it on the heavy side. Consider a 5lb trigger pull as a minimum pull weight. The trigger will wear because the surface hardening has been compromised. You will find your trigger will continue to lighten as it wears until it finally becomes unsafe.

Rock River Arms' two-stage match trigger is a base level match upgrade. It will give a very good trigger pull compared to stock. They aren't known for lasting forever like the standard like G.I. units, but will work a very long time for the average shooter. Keep your original trigger parts as an emergency back up.

Choosing the Right Trigger for You - Geissele Automatics and ALG Defense
http://m.youtube.com/watch?v=ypb5HXdDJhc

Just buy an ALG ACT or ALG QMS. Trigger jobs hardly ever work out well.

Thanks!

Boy, Springfield really pissed in his wheaties. But he came from a time when we didn't have all the cool shit that's available now.  Geissele really brought a quality match trigger to the forefront.

Geissele SSA trigger.......enough said.

I have one that lasted almost 4k rounds....then it went into double - triple and so on mode....kinda fun, but I'm shopping for a new one now....down to CMC and Timney.

I was following this thread because I have a PSA premium lower who's trigger is marginal at best.  After reading this I decided to polish it before I start spending more money.  Noticed that the trigger had raised material on the front and top side once I began polishing it.   Once I got it smooth and a mirror finished she dropped from 8.7lbs to 5.4lbs.  The pull is now super smooth and the break is as crisp as I have seen.

Researched case hardening and found it goes much deeper than the peak and valleys left over from machining so the concerns of polishing a trigger removes the hardening don't hold a lot of water unless you grind or sand more than a reasonable amount.

Maybe it will wear out faster, but then, maybe I just have a self tuned trigger that works better than someone else doing to.

And maybe while you are shooting at a public range it decides to go full auto and there is an off duty officer there.

Busted.

If you take off enough material to see a mirror finish on the sear surfaces that is absent of the original machining marks, you have likely gone to far. A little is a lot with an AR trigger job.

Correct, but then not all machining marks are the same, some are extensive and some minimal and no doubt you have to be very careful.

The depth of hardening is based on many things, such as process, time and temperature, and I have no idea what process, temp or time span the parts are hardened at.  So I did some research on case hardening and the first thing I learned is that the case hardening goes deeper than just a micro thin layer on the surface as some have suggested.  If it where true that case hardening is micro thin, just the wear from normal use would eliminate it in no time and expose the "soft" metal just as a scratch would.  Conversely, it most likely does not go deep enough to allow for the removal of a lot of material.

It would be very nice to have an expert in metallurgy and hardening opinion.

So don't polish a AR trigger because it will fail has been the advice forever. Explain to me how you can hone a 1911 trigger to 2 pounds or less and it will last with no change in trigger pull or running off but not an AR? Are AR triggers just made from junky soft steel?

Also, when this topic comes up the fan boys always rant about the ALG triggers. So my last LPK from PSA offered that option. I picked the cheaper one. It had a nice clean break, at about 10 pounds. The hammer spring is a monster. Makes the Wolf XP hammer spring look like a wimp. Both my PSA lowers with the standard LPK had better triggers. One of them much better. So apparently I am the only person who was ever disappointed with the ALG.

Then again, I have pulled every trigger Geissele makes and the only one I really thought was outstanding was the SD3G flat trigger. It was the best trigger I have ever pulled in a AR.

Because an AR trigger is only surface hardened. Plus this is not hypothetical, AR triggers that are polished have failed fairly regularly.

AGAIN!!! Google Bill Springfield trigger problems

If you want the best trigger I've ever pulled in an AR15 Without self modification:

On a 1911 it might make sense to do a trigger job since nearly every function of the trigger must be hand fitted. So smoothing out burrs would really help make a smoother trigger pull.

On a ar15, that sounds rather dangerous. The triggers aren't "custom" pieces that you put in. They're fairly standard. It would make a lot more sense to get a nice trigger and put it in yourself. I mean they are relatively cheap and require very little knowledge to install correctly.

They're not made from junky steel, it's just low carbon steel. Low carbon steel is hardened by adding carbon to the surface, which is what "case hardening" is.  It's a process that adds carbon to the surface, which hardens it. With AR triggers, that "case" is generally pretty thin. I don't know what the specs are for "Mil-Spec" triggers, but it would be fairly common for case hardened parts to have a case of no more than .005-.008   Many parts in mechanical devices are case hardened........parts in transmissions, rear ends in vehicles, etc.  Having the surface hardened while leaving the interior "soft" has properties that are beneficial for several reasons, although a trigger in an AR doesn't benefit from those properties that I can think of. A gear in a transmission might be case hardened to leave the interior "soft" which would then have the capability to flex a bit when under a heavy load, thus preventing the gear from shattering too easily.  A trigger in a 1911, if not susceptable to the same possible outcome of an AR trigger (short life from acclerated wear) has one of two conditions that I can think of. 1) it is also low carbon steel but with a very deep case (I know it is possible to have a case of at least 1/8" (.125))  The problem with that would be if you case harden something deeply, and it has areas of the part that are smaller/thinner than the depth of case, then that whole area would be expremely hard, which would make it prone to breaking.
2) the trigger on a 1911, if made from a tool steel, would be able to be heat treated, which would make the whole part hardened. THEN, the part is drawn back to a hardness that makes it both tough and wear resistent.
   I don;t know what steel 1911 triggers are made from, but obviously it is a different steel than AR triggers.  I might be wrong, but I think AR triggers are now made by a process known as MIM, which is Metallic Injection Molded. Similer to the way many plastic parts are molded.
   No matter how AR triggers are made, Mil-spec original style triggers are not ones that lend themselves to being honed on. YMMV

Now this good stuff.  Question I have is what keeps the normal wear at the contact point from removing the hardening over time?
I now see the merit of ALG trigger over polishing.  Thanks

Here's the thing with AR triggers.  The tolerances on the stock trigger are pretty tight.  For you to get any sort of decent trigger, you have to lessen the engagement surfaces and change some angles.  When you do that, the hammer doesn't catch the disconnector anymore, and the rifle can double on you when you let the trigger back out; that's both annoying and illegal.  Best option is just to save some pennies and buy a purpose built unit, then everything is right.

I have an ALG in my SBR and my SPR sports a RRA two stage. I was hesitant to buy the ALG and thought it wouldn't be worth the money I was spending, but it is a sweet trigger and so much better than the stock trigger.

This is a wicked witch.  Clearly polishing an AR trigger is not worth the risk if it compromises safety.
Yet at the same time, I still don't understand how normal wear doesn't remove the case hardening if its so thin.  Why don't more go full auto once the normal wear has removed the case hardening, or do they?

I went The JP reduced power trigger spring route. You avoid light hit by not using the reduced power hammer spring. However they didn't help that much. Ended up putting Geissele SSA-E in most of my AR's.