AR-15 and the "poor man's trigger job"

[AmbulanceDriver]

So at the Douglas Ridge Known Distance shoot last weekend, I experienced some serious malfunctions with my rifle.

Earlier, I had done the "poor man's trigger job" on both my AR lowers.   This involves snipping one of the legs off the hammer spring, which lightens the trigger pull significantly.  This also has the obvious effect of lightening the hammer strike. 

I had tested this modification with PMC .223 ammo, and it had actually functioned perfectly.   However, at the shoot last weekend, I used Federal XM193 ammo.  I was getting a 20-30% failure to fire rate.  Light primer strikes were the culprit.  I didn't have a spare hammer spring, so that night I bent the remaining leg on the hammer spring to increase the force on the hammer.   That reduced my failures to less than 1% (1 round out of the 120 round course of fire on Sunday). 

The moral of the story?   Make sure to test any modifications with ALL ammunition you might use. 

And I now have un-modified hammer springs in both my lowers.   I've polished the heck outta the engagement surfaces to smooth the trigger pulls.

And while it may not be cheap, a purpose built trigger is the more reliable way to lighten/adjust the trigger pull in an AR-15. 

[ThaiFighter]

interesting...

I've performed that mod on about a dozen AR's and not had an issue with any of them.  How much did you take off the hammer spring, and which leg? 

and just to show how two people can read the same story and derive a different moral...

"ALWAYS have spares!" 

[kenjo]

It costs more, but I put commercial aftermarket triggers in both my ARs. Function is flawless and accuracy much improved (the one I used at the last KD was 1 moa accurate out to 300 yds (the wind scattered the group a little at 400).



kenjo

[FiremanBob]

Also note that the case hardening in standard AR-15 triggers is thin, and attempting to stone the hammer hook will expose the soft steel. This will wear quickly to the point that the sear doesn't hold the hammer any more, leading to a dangerous and illegal problem.

Good triggers for ARs are expensive, but they are the way to go.

[fepowered]

ALG Defense makes improved trigger groups which start at about $45.  They bring the trigger pull down to about 6 lbs and improve the feel.  Rock River Arms are about $120 and are a 2 stage design which bring it down to about 4 1/2 lbs. 

[PaleRider]

I believe the best way to do this is to use the JP Enterprises Reduced Weight Trigger Springs (the yellow ones). I put these in my AR-15 last week and took it to the range. I've read many posts about people who have had problems with these springs, but many don't. They reduce pull on mil spec triggers to around 4.5 pounds. If they don't work for you, then you just reinstall the original HAMMER spring only, and you will still get a lighter trigger, just not as light as it could be. The kit is only $10, and you don't modify your original hammer spring.

[AmbulanceDriver]

ThaiFighter, I took the right leg on the hammer spring off.  That was the one that was recommended on the several pages worth of reading I did before I did this mod.   Also put a slight bend in the trigger spring, which lightened the trigger somewhat, but not as much as the snip on the hammer spring.  And yes.  The other moral of the story is definitely have spares on hand.   

And FiremanBob, I should clarify that the polishing was done with an ultra-fine stone.  Very careful not to remove much material at all, just smooth the roughness on the engagement surfaces in order to get rid of the grittiness in the trigger.

And I'm gonna have to start looking at the different options for the aftermarket triggers.   So far I've been looking at the Timney and Geiselle triggers, which are NICE but make my wallet cringe.

[ThaiFighter]

http://www.sargenthome.com/15_Minute_AR_Trigger_Job.htm

This is the one I've done over and over.   Trying to mod a few hammer springs to see if you can't get that relaiblity/lightness combo would be far more economical than dropping a pile on an am trigger. 

and a spare, of course...

[AmbulanceDriver]

Thai, that's the exact mod I did on both lowers.  And both lowers had a 20-30% FTF rate with the Federal XM193.  Zero failures with PMC ammo.

I may pick up a couple more spare springs and try to tweak them a little more for improved trigger performance while maintaining reliability. 

[Ninja Piper]

So at the Douglas Ridge Known Distance shoot last weekend, I experienced some serious malfunctions with my rifle.

Earlier, I had done the "poor man's trigger job" on both my AR lowers.   This involves snipping one of the legs off the hammer spring, which lightens the trigger pull significantly.  This also has the obvious effect of lightening the hammer strike. 

I had tested this modification with PMC .223 ammo, and it had actually functioned perfectly.   However, at the shoot last weekend, I used Federal XM193 ammo.  I was getting a 20-30% failure to fire rate.  Light primer strikes were the culprit.  I didn't have a spare hammer spring, so that night I bent the remaining leg on the hammer spring to increase the force on the hammer.   That reduced my failures to less than 1% (1 round out of the 120 round course of fire on Sunday). 

The moral of the story?   Make sure to test any modifications with ALL ammunition you might use. 

And I now have un-modified hammer springs in both my lowers.   I've polished the heck outta the engagement surfaces to smooth the trigger pulls.

And while it may not be cheap, a purpose built trigger is the more reliable way to lighten/adjust the trigger pull in an AR-15. 

I've got a spare trigger spring. PM me where you want it sent.

[Caliper]

I thought after snipping one of the legs of the hammer spring, one was supposed to bob the "tail" off the hammer to regain hammer velocity and keep a solid firing pin strike? 

[grunt soldier]

You can find the ALG QMS trigger for about 35 dollars shipped to your door. It's a complete milspec trigger that giessele's wife polishes up and makes them awesome. All grittiness is removed but about the same pull weight. They feel 10x better.  It's the cheapest most reliable option out there IMO and I run them on several of mine.

[Agrivere]

While it is painful when you buy it, I've used quite a number of triggers and for my money the geissele dmr trigger is worth the time and cost.  You can adjust both the first stage and the second stage to be whatever you want (more or less) and you can adjust the sear engagement to get a superb trigger break.  Expensive to be sure, but for me well worth it.

[jmdavis]

If you want a good match trigger. One of the best buy's is a Rock River National Match. This is around a 5 lb 2 stage trigger that is clean. Prices online range from $99-$129. I have been running one in my primary rifle since I built he lower in June of 2012. In that time it has handled 2000 rounds of 5.56 and another 5,000 rounds of .22lr from a dedicated upper, in addition to dryfire. It still makes weight for CMP EIC matches.

[Shooter30-06]

If you want a good match trigger. One of the best buy's is a Rock River National Match. This is around a 5 lb 2 stage trigger that is clean. Prices online range from $99-$129. I have been running one in my primary rifle since I built he lower in June of 2012. In that time it has handled 2000 rounds of 5.56 and another 5,000 rounds of .22lr from a dedicated upper, in addition to dryfire. It still makes weight for CMP EIC matches.

Plus one on this.  My Rock River 2 stage is very nice.

[Ninja Piper]

Rock River is a great trigger. I've installed several Gissele SSA triggers, as well as other Gissele models for customers and have been impressed with all of them. Granted, I don't make enough to actually OWN one of these triggers myself, but I do a lot of work with them! lol