Trigger pin walking out

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[ARCHIVED THREAD] - Trigger pin walking out

Posted: 10/9/2017 11:07:46 AM EDT

Built my 4th or so lower about a month ago and while shooting it this past weekend I noticed my trigger pin was walking out. It was causing the trigger to operate incorrectly and I noticed how easy it was to push the pin either way. I did some googling and people said make sure the hammer spring is in the groove(s) on the pin. I did what I could to try and make sure they were pushed down into the grooves but can't really tell.

Looks like a lot of people say the anti-walk pins out there aren't great. Would a small amount of locktite be a solution or should I buy a new pin?

Posted: 10/9/2017 11:21:28 AM EDT

[#1]

Either choice might work, you'd just have to try and see. Take a look at KNS trigger and hammer pins on Primary Arms or somewhere. That'd solve the problem too.

Posted: 10/9/2017 11:39:59 AM EDT

[#2]

I run KNS pins on every AR I own, it's cheap insurance.

Posted: 10/9/2017 11:49:55 AM EDT

[#3]

I've never had one assembled correctly have the pin walk out.

You are sure that assembly is correct?

Eta: make sure you have the legs of your hammer spring OVER the pin, not under. That usually fixes the problem.

Posted: 10/9/2017 11:58:09 AM EDT

[#4]

Quote History

Quoted:
I've never had one assembled correctly have the pin walk out.

You are sure that assembly is correct?

Eta: make sure you have the legs of your hammer spring OVER the pin, not under. That usually fixes the problem.

View Quote

This. That said, I've used KNS Anti-Walk pins, with perfect results.

Posted: 10/9/2017 12:07:01 PM EDT

[#5]

It shouldn't be walking out. There is enough tension on the pin with the hammer spring to keep it in place. Are you certain the hammer spring is installed correctly? One leg should be engaged in trigger pin grove top of the trigger pin.

It should look like this.

Attached File

Posted: 10/9/2017 12:15:40 PM EDT

[#6]

How about replacing your hammer/trigger pins & springs with parts that are in spec?

Edit: assuming you assembled it correctly!

https://www.brownells.com/rifle-parts/triggers-parts/hammer-parts/hammer-springs/ar-15-m16-m4-hammer-springs-prod41420.aspx

https://www.brownells.com/rifle-parts/triggers-parts/trigger-hardware/trigger-pins/ar15a4-hammer-trigger-pin-prod4519.aspx

Posted: 10/9/2017 12:44:09 PM EDT

[#7]

My pins have never walked out, but I did install these JP anti-walk pins which are slightly oversized, on the recommendation from QC10 on their 9mm Colt lower receiver. Probably not necessary, but it was relatively cheap insurance. If you find that your current setup is correctly installed, you might try these. You can find them basically everywhere.

Attached File

On my 5.56 SBR, I use standard pins and have had no issues, but on the 9mm, with the heavy bolt and harsh blowback action, I followed QC10's suggestion.

Posted: 10/9/2017 1:01:09 PM EDT

[#8]

Quote History

Quoted:
I've never had one assembled correctly have the pin walk out.

You are sure that assembly is correct?

Eta: make sure you have the legs of your hammer spring OVER the pin, not under. That usually fixes the problem.

View Quote

This right here. I run KNS pins in all my 80% lowers, but in a regular anodized lower its fine without. That said, with anti-walk pins you are only out like $20-30 for a set of KNS, cheap peace of mind if you want it.

Posted: 10/9/2017 3:30:27 PM EDT

[#9]

The hammer spring legs are on top of the pin for sure. It's hard to see if the spring legs are actually in the groove honestly so I can't guarantee that. I've never had this issue either. The weapon is as suppressed ar pistol with a 10.5 barrel making me think the blow back is a little more violent than a carbine length + gas system.

I haven't shot it since reinstalling the pin so it may be okay. I probably shot 50 rounds through it before the pin stalking walking.

I'll look into kns pins if the problem still persists.

Probably can't see anything

but here is a picture.

Posted: 10/9/2017 6:14:33 PM EDT

[#10]

Make sure the spring is installed correctly also

Posted: 10/9/2017 6:35:47 PM EDT

[#11]

Quote History

Quoted:
Make sure the spring is installed correctly also

http://oi43.tinypic.com/2hd1kqb.jpg

View Quote

It's installed correctly. I've made that mistake before. The hammer spring legs are "strained" against the hammer pin.

I went ahead and ordered one of the KNS anti-roll pin sets so I can nip this in the bud.

Posted: 10/9/2017 7:23:03 PM EDT

[#12]

Quote History

Quoted:
I run KNS pins on every AR I own, it's cheap insurance.

View Quote

This for me as well. 5 AR's and counting.

Posted: 10/9/2017 8:22:47 PM EDT

[#13]

Quote History

Quoted:

This for me as well. 5 AR's and counting.

View Quote

KNS pins are anti rotation pins, not anti-walk pins. There’s a limit to which KNS pins will resist walking in a lower that has problems, either because of the lower itself of the parts in it.

Properly installed and in-spec FCGs should not allow pins to “walk.” Before a bandaid is applied, maybe it would be a good idea to figure out what the actual culprit is.

Posted: 10/9/2017 8:31:14 PM EDT

[#14]

Doesn't the kns anti-rotate pin kit come with parts including two screws that physically hold the parts in place?

If you read reviews on the kit people talk about having problems with pins walking and this fixed it.

Posted: 10/9/2017 9:23:53 PM EDT

[#15]

The screws tighten into the trigger pin, the hammer pin is held by the tension of the trigger pin screws. The hammer pin is solid with a "boss" on each side that fits into the rail.

Posted: 10/9/2017 9:49:04 PM EDT

[#16]

Quote History

Quoted:
Doesn't the kns anti-rotate pin kit come with parts including two screws that physically hold the parts in place?

If you read reviews on the kit people talk about having problems with pins walking and this fixed it.

View Quote

They do and they physically can't walk with the KNS Kit.

Posted: 10/9/2017 10:32:59 PM EDT

[#17]

Quote History

Quoted:

They do and they physically can't walk with the KNS Kit.

View Quote

That's what I figured, thanks.

Posted: 10/9/2017 10:35:32 PM EDT

[#18]

I have a lower I bought around 96 or 97. Shot it a bunch and one day trigger pin walked out. Thought I did something wrong. Cleaned inspected and it walked out again. Put one of those old anti walk pins in it Bushmaster use to sell with the C clip on it. Probably a worn pin. I never tried another in it.

Posted: 10/9/2017 11:08:50 PM EDT

[#19]

Is your trigger pin grooved like it should be. I've seen a few pins with no grooves, obviously defective. Although they'll fix it, before installing the KNS pins, I would see what's causing the issue to begin with if for nothing more than to satisfy my own curiosity.

Posted: 10/9/2017 11:13:19 PM EDT

[#20]

Quote History

Quoted:
Is your trigger pin grooved like it should be. I've seen a few pins with no grooves, obviously defective. Although they'll fix it, before installing the KNS pins, I would see what's causing the issue to begin with if for nothing more than to satisfy my own curiosity.

View Quote

It has one groove in it. I've seen some pins with two and some with one. I agree, I'd like to figure out what is causing it but what I am going to do is install the kns pins nad shoot the hell out of it. If my fcg is installed correctly I can only imagine it's a clearance issue as someone else point out which I'm not worried about.

It initially was a little scary as I fired a round and when I went to reset the trigger it fired another round.

Like the echo trigger.

Posted: 10/9/2017 11:14:22 PM EDT

[#21]

Quote History

Quoted:

It has one groove in it. I've seen some pins with two and some with one. I agree, I'd like to figure out what is causing it but what I am going to do is install the kns pins nad shoot the hell out of it. If my fcg is installed correctly I can only imagine it's a clearance issue as someone else point out which I'm not worried about.

It initially was a little scary as I fired a round and when I went to reset the trigger it fired another round.

Like the echo trigger.

View Quote

Yeah, not good. Good luck.

Posted: 10/10/2017 10:50:55 PM EDT

[#22]

Quote History

Quoted:

It has one groove in it. I've seen some pins with two and some with one. I agree, I'd like to figure out what is causing it but what I am going to do is install the kns pins nad shoot the hell out of it. If my fcg is installed correctly I can only imagine it's a clearance issue as someone else point out which I'm not worried about.

It initially was a little scary as I fired a round and when I went to reset the trigger it fired another round.

Like the echo trigger.

View Quote

There are some oddball pin sets out there (I've had one myself). Some have specific pins (center groove on hammer pin, single side groove for trigger pin), but most are "universal" pins (work for either hammer/trigger) that will both have either two or 3 grooves (both having center hammer groove, and both having one (or both) side groove for the trigger.
If I were you, I'd just try a different brand of pins and make sure they have multiple grooves, or make sure the corresponding groove pins are in the proper location.

Posted: 10/11/2017 3:41:54 PM EDT

[#23]

Loctite will not work, it is a anerobic chemical that only dries in the absence of O2

[ARCHIVED THREAD] - Trigger pin walking out

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