DIY Trigger job

[agksimon]

If someone wants a two pound trigger for benchresting, it's fine to pay $100-$200 for one. If you are happy with a smooth, crisp, 4 pound pull, smooth the sear and hammer contact surfaces with 330 grit then 1000 grit sandcloth, on, a flat hard stone and wrapped over a thin file, being very careful to keep all surfaces flat and straight. Add a JP Spring kit for $11 shipped and you've saved a lot of money. I've done dozens of them for the guys I shoot with. If done correctly, it will leave the trigger just as safe as any custom trigger.

 

[MistWolf]

AR triggers are case hardened and the thickness of the case hardening can be rather thin. Cutting through the case hardening will expose the softer steel underneath. The softer steel will wear quickly, leading to doubling and tripling. This is why it's inadvisable to do more than a very light polishing of an AR trigger and with the utmost caution.

Lightening the hammer spring can cause light primer strikes. The action of cocking the hammer helps control carrier speed. Lightening the hammer spring reduces the force needed to cock the hammer and there will be an increase of carrier speed.

 

[Pisgah]

All I'll say is -- that's a quick way to end up with a surprise full-auto.

 

[agksimon]

AR triggers are case hardened and the thickness of the case hardening can be rather thin. Cutting through the case hardening will expose the softer steel underneath. The softer steel will wear quickly, leading to doubling and tripling. This is why it's inadvisable to do more than a very light polishing of an AR trigger and with the utmost caution.

Lightening the hammer spring can cause light primer strikes. The action of cocking the hammer helps control carrier speed. Lightening the hammer spring reduces the force needed to cock the hammer and there will be an increase of carrier speed.

That's why I polish them and don't remove more than a tenth or two.

I use the JP spring sets with the red, hammer reliability spring in it. I use military ammo with hard primers and have never had a misfire and neither has anyone I've done this for. You can get a the yellow hammer spring that is even lighter, but they can have light strikes on hard primers.

 

[agksimon]

All I'll say is -- that's a quick way to end up with a surprise full-auto.

That may be possible, if you don't know what you're doing. I've had a lot of experience and worked with a few professional gunsmiths over the years and I'm very competent at what I do. I use a lot of tools that most people don't have, including a lighted magnifier and a full set of honing stones.

 

[MistWolf]

When posting about stoning AR triggers, it would be a good idea to post warnings to about cutting through the case hardening and that it could lead to runaways if done incorrectly. Not everyone perusing these forums have years of experience and specialized tooling.

 

[Rastoff]

It may result in a potentially unsafe trigger, but I don't think it would go full auto. For it to go full auto, the disconnect will have to fail. If you only stone the sear, the disconnect will function fine.

Even if the hammer were to simply follow the BCG, it wouldn't fire.

 

[MistWolf]

There have been reports from reliable sources that when the case hardening is removed the sears wear at an accelerated rate, leading to doubling, tripling and in some extreme cases, runaways.

 

[bamashooter]

Is there something inherently peculiar to AR mil-spec hardened fcg parts as compared to several other firearms, for example even the cheapest 1911 parts? I can't find hard consistent data to support the opinion that the "hardness" is so thin it has only one side to it. What is the thickness and who can produce that spec? I have found references to thicknesses of 0.008"-0.012" which sounds reasonable and 1.0mm-1.5mm which sounds a bit much to me.

Though I have nice aftermarket triggers, I live among a bunch of "good ol' boys" who demonstrate superior mechanical knowledge, skills, and abilities on anything ranging from mowers to turbine engines. Hundreds.

Well over 1,000 ARs within spittin' distance of me. The vast, vast majority of ARs (in my area) are the older Bushmaster, DPMS, and assorted M&Ps with no shortage of franken-builds. Of those you'll find perhaps 50% maximum which have not had the parts lightly stoned, sanded, emery clothed, assorted compounds used from pearl drops toothpaste to semichrome, to flitz. Along with spring "upgrades", etc.

I have both witnessed and participated in these cleanup sessions and honestly can't recall any instance of a malfunction due to a little fluff and buff, exaggerated parts wear to the point concern. And these rifles get used regularly from varmints, hunting, and in the past years wild pigs/hogs. In fairness I have seen actual grinding / "coarse" filing take place to the point I would order new parts for the "victim".

I guess I could see where if someone didn't grow up with tools in their hands and have a decent working knowledge of some level of machining, be it trade school, employment, picked it up on the farm from pop, grand pop, etc, they could easily screw something up.

Speaking of this general topic, anyone here remember Kasenit or hardening with nasty, dirty, filthy (high carbon content) motor oil?

My point being, I don't find the AR being a sensitive firearm equipped with wussy-like fcg parts as seems to be the general consensus in most forums I frequent or monitor from time to time.

 

[ChattanoogaPhil]

Hey Guys

There's been a lot of threads in the Concealed Carry and Self Defense section about modified triggers and possible legal complications. They're usually contentious discussions and don't end well. Let's keep things in this section more focused on the rifle rather than courtroom.

 

[cyphertext]

Question withdrawn, your honor...

 

[ken158]

All I'll say is -- that's a quick way to end up with a surprise full-auto.

Not really... it may double but the disconnector will catch it.

 

[Rastoff]

Is there something inherently peculiar to AR mil-spec hardened fcg parts as compared to several other firearms, for example even the cheapest 1911 parts?

An excellent question. I don't have the definitive answer, but I can lead us in the right direction.

I found this about hardening steel...

surface hardening of steel can have an advantage over through hardening because less expensive low-carbon and mediumcarbon steels can be surface hardened with minimal problems of distortion and cracking associated with the through hardening of thick sections.

Got that from here: https://www.google.com/url?sa=t&rct...ee32a98280d5&usg=AOvVaw0udgnkEY2FWZD91Yz4Hs-7
This leads me to believe, based on the mountains of discussions that talk about how thin the AR sear is hardened, that manufacturers only surface harden the parts to save time and money. A through hardened sear/trigger would be 3 times as expensive to make. It would also make the sear more brittle which presents its own problems.

 

[C J]

I guess I could see where if someone didn't grow up with tools in their hands and have a decent working knowledge of some level of machining, be it trade school, employment, picked it up on the farm from pop, grand pop, etc, they could easily screw something up.

I grew up on a farm where you had to learn to do pretty much everything yourself if you expected to make farming pay but this level of work is well beyond what I learned on the farm. Most things I can do pretty well when it comes to working with tools but this is something that really should only come from being shown how by someone that knows IMO. There's a potential for bad things to happen otherwise. That much seems pretty certain whether it's a runaway or more likely a failure which means a replacement trigger anyway.

 

[rockquarry]

Just something to consider; not looking for a debate ...trigger pulls on ARs and many other guns straight-out-of-the-box are heavier than some like, granted. However, it's worth the effort to shoot such guns for at least a couple of hundred rounds or so using a good benchrest setup and also shooting offhand from various stances, always mindful of good trigger control.

I've found ARs are capable of pretty good groups with stock, unmolested triggers. After giving such a gun a fair workout with accurate ammunition and the trigger is horrible and completely unacceptable, that's the time to have a competent person fix or replace it.

However, many today erroneously reason that a light trigger and/or a high magnification scope are shortcut routes to good shooting. The same people choose to ignore learning good shooting skills and benchrest technique. Trigger jobs, replacement triggers, and high powered scopes are specialty items that provide real advantage only to those who have already learned to shoot well.

 

[Rastoff]

The major beef with a GI trigger on an AR is not the pull weight, but the grittyness and extreme creep. They are gritty because they're cheaply made. The creep is excessive to ensure positive safety.

Gritty is easily changed by polishing with the 15 Minute Trigger Job method (look it up). Changing the creep without changing the whole trigger is more dangerous.

 

[rockquarry]

I referred to "pull weight" as a catch-all phrase for a real or perceived bad factory trigger; certainly a poor choice of words on my part.

 

[WR Moore]

Most, if not all, the parts in the AR fire control system are cast. So, quality depends upon quality of the molds, material and temperature control as well as any finishing and heat treat. And yes, some are better than others.

As someone noted above, with many parts of small dimension and/or complexity, case/surface hardening is superior to through heat treat. The metal used also affects this. Dunno what the specs are for the fire control group, but they're generally considered low stress parts. Therefore, you're not going to see high grade alloys used.

I used the term "cast" above to cover several methods that produce similar results: casting, sintering and MIM. I've worked with a number of MIM parts and all those I've seen have be extremely well done with excellent metal quality and hardening to surprising depth. Can't say the same for sintered parts.

Some good points have been made about people expecting widgets/money/light trigger pulls to compensate for actually learning to shoot. Dry firing can greatly improve trigger quality. I experienced mandated transition training to two different semi-auto pistols. The triggers started out gritty, after 3-5 days and beau coup rounds, they were much improved. You don't need to actually expend ammo to get the same results. Yes, a very few triggers can benefit from some extremely light stoning to speed/finish the process.

 

[agksimon]

If you look under a lighted magnifier, you will see why inexpensive triggers have a gritty feel to them. The contact surfaces are given the final touch with what looks like a surface grinder, which leaves micro-blemishes in the surfaces. Using a much finer grit leaves a highly polished surface and gets rid of the gritty feeling.

 

[MistWolf]

The major beef with a GI trigger on an AR is not the pull weight, but the grittyness and extreme creep. They are gritty because they're cheaply made. The creep is excessive to ensure positive safety.

This is very true. My biggest gripe with the standard trigger is the hop, skip and a jump pull they have right out of the box. Every standard trigger I have, I removed from the lower, cleaned and lubed with grease. This improves the pull greatly. So far, each one has smoothed out with dry firing & shootinging. The creep is still there, but with the pull smoothed out, I find the creep isn't so bothersome.

Gritty is easily changed by polishing with the 15 Minute Trigger Job method (look it up). Changing the creep without changing the whole trigger is more dangerous.

A light polishing with some rouge shouldn't hurt a thing and will cure most of the roughness. Just hit it lightly and let lubing, dry firing and shooting do the rest.

You're very right about shortening the creep.

 

[Steve912]

I've found ARs are capable of pretty good groups with stock, unmolested triggers.

<snip>

However, many today erroneously reason that a light trigger and/or a high magnification scope are shortcut routes to good shooting. The same people choose to ignore learning good shooting skills and benchrest technique. Trigger jobs, replacement triggers, and high powered scopes are specialty items that provide real advantage only to those who have already learned to shoot well.

Amen, to all the above.

That, and they just gotta have something to list in
the sig file!!!