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Posted: 2/8/2006 2:38:55 PM EDT
[Last Edit: 2/10/2006 4:42:14 AM EDT by ipschoser1]
I thought ya'll might be interested in a cheap, reliable 4# trigger for your AR. Right up front, I'll conceed, the following proceedure isn't suitable for duty/military rifles. It's obviously not suitable for select fire triggers. It is, however, fine for competition, hunting and range rifles. I make no claims about being a gunsmith. What I am is a competition shooter with a good understanding of AR trigger functioning/dynamics. IF YOU'RE NOT MECHANICALLY/TECHNICALLY INCLINED, FIND A GUNSMITH TO INSTALL AN AFTERMARKET TRIGGER FOR YOU. For the most part, the AR trigger group is a simple, straight forward arraingement that lends itself well to competent mods. Proceed at your own risk though...

Stock AR triggers are meant to be absolutely reliable under any condition imaginable. They are intended to pop hard, milspec primers after landing on the beach or under arctic conditions. They are also meant to be lawyer proof when some idiot AD's thru piss poor gun handling.

Most of us practice good gunhandling skills and would prefer a clean breaking, light trigger to extreme conditions reliablity. It suits our uses MUCH better. The following is an inexpensive alternative to expensive aftermarket triggers and offers performance almost on par with many of them.

This proceedure is a hand fitting operation that requires assembly/disassembly several times during the process. It's not difficult, but takes some time and patience. The results will be worth the effort!

Let's start with the hammer. Since a light trigger requires the use of a lighter hammer spring, the hammer itself needs to be lightened to maintain ignition reliability. Reliable ignition is a function of hammer SPEED, not mass, with the light spring installed. I recommend JP hammer/trigger springs. The pics following show the modified parts on the left. I photoed them with the JP yellow springs installed for clarity. Hammers can be modifyied using a Dremel tool and a carbide cut off wheel. Cold blue as necessary.

Modified "speed" hammer:


Next, a 1/4x28 set screw is installed into the grip screw hole to push up on the trigger and eliminate the "pretravel" problem inherent in a stock trigger. Stock units have HUGE sear engagement and actually cam the hammer back considerably on firing. This is what we aim to remove with the set screw. When we get everything "just right" the set screw will be removed and reinstalled with blue LocTite. It must be chemically clean for this step.

Set Screw installation:


When the set screw is initially installed, the rear of the trigger will have to be ground to allow clearence between it and the safety. When properly set up, a modified rifle will have a "hard" safety. This doesn't mean that it's hard to operate, but rather that there's very little clearence between the safety and the trigger when the hammer is cocked and the safety is "on". Remember, we removed the excessive sear engagement with the set screw. Grind the rear of the trigger carefully. Reinstall it often to check for proper fit. IF YOU GRIND TO MUCH, THE SAFETY WILL NOT FUNCTION PROPERLY AND THE TRIGGER WILL BE UNSAFE! The only cure for an overground trigger is a new part. Be careful. Polish the hammer and trigger engagement surfaces with Flitz compound. The idea here is a smooth finish, not to change any angles or dimensions. The surface hardness of the parts is only a few thousandths of an inch thick. If you go thru the hardened part, the trigger job will not hold and the rifle will begin to "double" as the parts wear excessively. For this reason, don't use anything except a polishing wheel and Flitz or stones for working the engagement surfaces.

Modified trigger:


Sometimes, when the sear engagement is reduced to reasonable levels, the disconnector won't release the hammer after a shot is fired and the trigger is released. Some trigger jobs require modifying the disconnector "nose" to allow adequate clearance. This is done by carefully removing material until the disconnector will release the hammer properly. Be sure to keep the angles of the nose perpendicular as shown below.

Modified disconnector:


Another veiw of the disconnect mods:


When the modified trigger is installed, LocTite the set screw in place. Allow 24 hrs for the LocTite to cure before firing the rifle. With a cocked hammer (unloaded rifle) and the safety "on", the trigger should be pulled to see if the hammer falls. Obviously, it should not. Sear engagement in the above proceedure is a common sense judgement. The trigger should break clean but not be a "hair" trigger. The hammer should not fall when the unloaded rifle has the muzzle or stock bumped on the floor (wood block).

The resulting trigger from the photos isn't quite in the league with my full JP trigger in another rifle, but it's a HUGE improvement on the stock unit. It breaks clean at 4 lbs and has been totally reliable.

ETA an link to a downloadable pdf version Punani was kind enough to provide. Punani's pdf version
Link Posted: 2/8/2006 4:17:30 PM EDT
[Last Edit: 2/8/2006 4:20:40 PM EDT by ALAN308]
Very nice post, thanks.
How long a set screw is best ?

ETA; I use 2000 grit wet/dry with solvent and a flat surface on the surfaces. [It is fast]. As stated, great care here.
Link Posted: 2/8/2006 5:30:05 PM EDT
[Last Edit: 2/8/2006 5:35:22 PM EDT by 3-gun]
A 1/4" long set screw will do the trick. You will also need to cut a little off the grip screw. If the moon is full and all the Planets are in line, the trigger pull may go to @3.5 lbs or so. I had well over 10,000 rds through mine with no problems. I would not use anything more than a hard stone for 3 to 5 passes and some flitz on a felt wheel.
Link Posted: 2/8/2006 5:55:40 PM EDT
Yep a 1/4" to 5/16" set screw will do fine. They can be purchased at Lowe's or Home Depot.
Link Posted: 2/9/2006 7:18:36 AM EDT
tag for later
Link Posted: 2/9/2006 7:31:58 AM EDT
This hasn't been posted in some time: www.geocities.com/molonlaberkba/triggerjob.html

Have used this method on several ocassions, it works well abeit not as extensive as the method above.

Mike
Link Posted: 2/9/2006 7:41:16 AM EDT
tag!
Link Posted: 2/9/2006 3:13:10 PM EDT
Also,not all lowers are tap'ed all the way through the grip screw hole. You may have to run a finish tap through before you can use the set screw.
Link Posted: 2/9/2006 5:49:53 PM EDT

Originally Posted By 3-gun:
Also,not all lowers are tap'ed all the way through the grip screw hole. You may have to run a finish tap through before you can use the set screw.



Fortunately, I haven't run into that yet. I've done work on Colt, Bushy and RR lowers. You had a Bushy that wasn't drilled thru though, right?
Link Posted: 2/17/2006 5:18:44 PM EDT
Link Posted: 2/18/2006 3:48:44 AM EDT
Thanks for taking the time to post this.
Link Posted: 2/21/2006 2:02:31 PM EDT

Originally Posted By usagold:
Thanks for taking the time to post this.



You're welcome. Hope you can use the info.
Link Posted: 2/28/2006 8:14:50 AM EDT
Tag-a-roni
Link Posted: 2/28/2006 10:44:36 AM EDT
Link Posted: 3/1/2006 8:25:58 AM EDT
Is the set screw a bolt inside of a bolt similar to a "sex bolt"? I can't find one at any hardwares, Lowe's or Home Depot. I did find a binding post screw that I could probably get to work.

Thanks,

Jeff
Link Posted: 3/1/2006 11:28:02 AM EDT
.
Link Posted: 3/1/2006 11:37:13 AM EDT
taggage
Link Posted: 3/1/2006 2:44:26 PM EDT

Originally Posted By jjrobo:
Is the set screw a bolt inside of a bolt similar to a "sex bolt"? I can't find one at any hardwares, Lowe's or Home Depot. I did find a binding post screw that I could probably get to work.

Thanks,

Jeff



Yes, it's an internal wrenching type set screw that accepts an allen wrench. Usually, at Lowe's or HD, they are in the hardware section in the pull out drawers...
Link Posted: 3/1/2006 2:47:20 PM EDT

Originally Posted By gunslingerdoc:
On can also bend one leg of the hammer spring to decrease the trigger pull - I have done this with several companies match triggers and had good results - lighter pull and no ignition probs even with foreign surplus ball. You can also shorten on of the legs by about 1/2 for the same effect.



Early JP triggers used a stock hammer spring with one leg cut off for a 50% spring rate reduction. You had to be careful to intall it correctly so that the leg of the spring that was left was on the proper side to engage the retaining notch in the trigger pin...
Link Posted: 3/1/2006 6:14:35 PM EDT
I did some tests the other day with some springs. I have a RRA LPK installed. i used the JP yellow springs and a set of springs from Yellow Tavern. nothing was polished at all and less than 100 rounds on the LPK. Here were my findings using a Lyman digital scale average of 10 pulls.

Standard RRA 8 lbs 6 oz
JP springs 4 lbs 10.3 oz
Yellow Tavern springs 5 lbs 14.5 oz
RRA 2 stage 5 lbs 4 oz

i was a little shocked at the RRA 2 stage. ya always here 4.5 lbs but its about a pound more than ya here.

here is the same principle of the setscrew in teh pistol grip screw hole.


im thinking of drilling and tapping a scew on the lathe to duplicate the above.
Link Posted: 3/1/2006 6:31:14 PM EDT

Originally Posted By machinehead:
I did some tests the other day with some springs. I have a RRA LPK installed. i used the JP yellow springs and a set of springs from Yellow Tavern. nothing was polished at all and less than 100 rounds on the LPK. Here were my findings using a Lyman digital scale average of 10 pulls.

Standard RRA 8 lbs 6 oz
JP springs 4 lbs 10.3 oz
Yellow Tavern springs 5 lbs 14.5 oz
RRA 2 stage 5 lbs 4 oz

i was a little shocked at the RRA 2 stage. ya always here 4.5 lbs but its about a pound more than ya here.

here is the same principle of the setscrew in teh pistol grip screw hole.
www.brownells.com/Images/Products/072000001.jpg

im thinking of drilling and tapping a scew on the lathe to duplicate the above.



I think you'll find that once you take the pretravel out (set screw), you'll see the numbers on the JP spring equipped fire control group come down to around 4#. As 3 gun noted above, on some lowers, it may be possible to go as low as 3.5, but it's not the norm. Without the pretravel you'll also obviously have a much cleaner break. Thanks for posting the numbers. A budget trigger job can compete with some of the aftermarket triggers.
Link Posted: 3/1/2006 7:02:15 PM EDT
tag
Link Posted: 3/1/2006 7:13:06 PM EDT

Originally Posted By mr_wilson:
This hasn't been posted in some time: www.geocities.com/molonlaberkba/triggerjob.html

Have used this method on several ocassions, it works well abeit not as extensive as the method above.

Mike



I purchased a used lower that the method linked in your post shows. The trigger pull was the worst of any of my stock triggers. I pulled it apart and the sear surfaces were damaged badly, and the rear of the hammer was cutting deeply into the disconnector. After you stack up a round count, take yours apart and inspect it.

A guy, here, on this board does a nice trigger job really cheap, and is done on a proper jig. I sent him two and they are great. Cheap enough that all of this tinkering mentioned is just not worth it, considering the potential damage and liability.

There is too much at stake to screw this up.
Link Posted: 3/1/2006 7:30:19 PM EDT

Originally Posted By wildearp:

Originally Posted By mr_wilson:
This hasn't been posted in some time: www.geocities.com/molonlaberkba/triggerjob.html

Have used this method on several ocassions, it works well abeit not as extensive as the method above.

Mike



I purchased a used lower that the method linked in your post shows. The trigger pull was the worst of any of my stock triggers. I pulled it apart and the sear surfaces were damaged badly, and the rear of the hammer was cutting deeply into the disconnector. After you stack up a round count, take yours apart and inspect it.

A guy, here, on this board does a nice trigger job really cheap, and is done on a proper jig. I sent him two and they are great. Cheap enough that all of this tinkering mentioned is just not worth it, considering the potential damage and liability.

There is too much at stake to screw this up.



I had well over 10,000 tounds through my colt and the trigger parts looked as good as the first day it was done.
As IPSC said, you need a little understanding of what your doing. If the sear surfaces were damaged, someone used too much stone. You only need to POLISH the hammer and sear.
This post is not for everyone, a lot of people are much better off having a gunsmith put in a JP, RR etc. , or just staying with a 12lb stock trigger. JMO
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