trigger pins for AR-15?

[loose noose]

I recently installed a Timney Trigger in a DPMS AR-15 for a friend. The problem is when the hammer is in the cocked position, the two pins that hold the trigger/hammer in place tend to work their way out. However when the hammer is forward the pins stay put.

I installed a Timney in my Bushmaster, with no such problem, on my friends I put a dab of blue Loctite on the pins, and so far it appears to have solved the problem.

I'm wondering if MilSpec pins might resolve the problem completely, has any one else had this problem?

Note I did secure the two set screws on either side of the trigger/hammer assembly. BTW I've done quite a few AR-15s but this is my first DPMS that I've done.

 

[DJW]

One of the aftermarket suppliers used to make pins with a groove around the pins and a circlip was used to secure the pins and prevent them from traveling.
I know a few guys who used a dab of JB weld to accomplish the same thing.

 

[loose noose]

I'm still wondering why the factory trigger and hammer seemed to secure the pins in place. I told my buddy to go and get some milspec pins from Numerich gun parts and we would try them.

I don't like to put a glue on what is supposed to be a competition trigger, for fear of messing it up. I've never been fond of DPMS, as I don't believe they use milspec parts in assembling their firearms IMHO.

 

[BBBBill]

Done lots of Timneys, but never done one on an AR. Are the trigger lock (set) screws supposed to engage the pin in the circular grooves where the spring legs used to fit? Edit

Timney does state to NOT use Loctite on their trigger. http://timneytriggers.com/index.php?option=com_content&view=article&id=13&Itemid=81

 

[loose noose]

BBBill, The set screws go just below where the hammer springs go, infact you have to hold the spring off to the side in order to get the set screw (provided allen wrench) started (using a small screw driver), after you have both set screws tightened down, then you can put the pins in. Both pins are the same diameter (small) .154.

On those set screws they don't recommend using any Loctite, primarily because the long arms of the springs (two) sit over the set screws and would prevent them from coming out. The only place I used the Loctite was on the pins themselves to keep them from falling out.

Now the trigger pull breaks right at 3#s but I don't like the idea of the those two pins likely to fall out after a day of shooting.

 

[BBBBill]

My main point is that I think the set screw is supposed to engage the groove in the pin where the spring leg would have gone with a conventional trigger. It may be loosening without some thread locker. I don't think you will have a problem with careful use of Loctite as you did. Their main concern is probably fear of someone getting it into the operating parts and mucking it up. The captive pins are still on the market. Brownells carries the KNS pins (.155", about $30-33) and JP Enterprises (.156", about $10). You can use a pin gage (or drill bit shank) to check the hole sizes in the frame and trigger pack to get the best fit.

 

[loose noose]

BBBBill, thank ya for the info. I'll have to give that to my buddy especially the JP Enterprises, I thought about using an old drill bit and cut it down to give it a nice firm fit, won't see him until next weekend, but I'll run that by him too.

 

[Dallas Jack]

The allen screws do not line up with either pin. When installing you should put the pins in first and then the allen screws. They contact the bottom of the lower reciever putting upward preasure on the pins. My WAG is that either the pins are under sized or the holes are over sized. The correct sized pins should fix the first problem. KNS anti-walk pins should fix either problem.

Let us know how it comes out.
Dallas Jack

 

[Dallas Jack]

Forgot something. You should have 4 allen screws. The first 2 screw down against the lower, the second set go on top of them to keep the first set from backing out.
Dallas Jack

 

[loose noose]

Dallas Jack, not on the AR-15, the skeleton trigger as well as the competition trigger both come with just two allen screws, as the hammer springs, one on each side keep the screws in place and prevent them from coming out.

Actually it is a pretty simple task taking the old hammer and trigger out, and replacing it with the Timney Trigger. I've done this on two of my AR-15s as well as on many others. The only problem is I've never done it on a DPMS model before, and I measured the pins to make sure they were the small size, before my buddy ordered the trigger assembly.

This weekend I'm going to check with him and see about using an old drill bit for a pin, and see if that don't solve the problem.

 

[Dallas Jack]

Loose Noose, the problem with the screws is not them coming out but that they must remain tight. As long as they are tight against the lower they should capture the pins. The screws and the hammer springs are unrelated.

If he has the trigger out look to see if the screws pass completely (freely) though the trigger housing. It is possible they are binding and not tightening completely against the lower.

My AR Timney is the skeleton version. I had to send the first one back because of doubling issues. The replacement came with 4 screws and instructions to install the second set over the first.

I bought mine 6-7 years ago and things may have changed abit. I looked at Timneys installation instructions at their site and there was no mention of the second set of screws.

Good luck, hope you get it sorted out.
Dallas Jack

 

[nyresq]

The set screws need to be locked down to hold tension agains the pins.

A set of the KNS captured pins is also another solution...

 

[BBBBill]

I took another look at the instructions and realized that the set screws do not bear on the pins, but instead bear on the bottom of the receiver. The pin serve to locate the trigger module and the set screws wedge against the bottom causing the walls of the tubes in the module to side load the pins in the receiver. Those set screws must be tight and locked in place to keep the pins from walking out. Loctite on the ends of the pins is not a bad idea, but since the pins play no roll in the trigger pull in this application, I think I would also go with least expensive captive pins that will fit the receiver/trigger pack and call it good.

 

[loose noose]

BBBBill, We just took it out and shot the dickens out of it this morning, over 100 rounds, and the pins are staying put, so I believe we're going to leave it alone for the time being. I do appreciate all the info. I received on this though. I still believe it has to do with the DPMS model, never had any problems with Bushmaster, A-1s, Palmetto, or any of the others I've done. Come to think of it, I don't believe the pins were in it all that tight to begin with, note this was a brand new gun I just found out?!

 

[ErikO]

KNS pins are my suggestion as well. Anti-walking pins will not walk.