What causes an ar hammer pin to walk from L to R during firing

[Dustbuster]

per topic. springs seated, lubed pins what causes a pin to walk from the left side to the right? Ive heard its more of an issues w bursts on auto,but am curious...of course all input appreciated!

[173rdABN]

Wear from excessive use. Pin holes enlarging over time (ever so slightly but enough to have less tension on the pins as well as springs loosing tension to hold the pins in). I've only had one m4 ever do that to me, and that was in the army. Never have I seen it happen otherwise.

Edited May 13, 2014 by 173rdABN

[Clod Stomper]

Don't know about the cause without seeing it. Probably what 173rdABN said. But KNS anti-walk pins should fix it.

[Dustbuster]

New rifle,under 1000 rounds through it. Did go the kns route.... Hiperfire 24c trigger, last one I had happen was on a stock sig 516 rifle...both mfg's sent me new pins. Springs were seated right, all was lubed right, just weird


Sent from my iPhone using Tapatalk 2 of course it ate my spelling. Edited May 13, 2014 by Dustbuster

[Tuffus]

I had one to do that once. The hammer spring was installed upside down. I flipped it over and no more problem.

[Smith]

Bad design ;). They hope that spring tension combined with hole size will hold them. Eventually that tension will wear the hole and they will walk. Sometimes the pin holes are a slightly larger than they need to be and the issue shows up sooner.

 

 KNS pins work well and you don't have to worry about it.

[Dustbuster]

The only things I can think of is of course wear, and poor tolerance control. Another thought was w mfgs using coatings on parts, if you had a coated part with a hole and a coated pin,the amount of play may increase when the coatings wear off of the metal components.In my case it's happened in newer rifles, I just want to know why they walk....


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[gregintenn]

I agree with the spring installed upside down.

[molonlabetn]

Most often, especially if it was a self-build, the hammer spring is in backwards... As others have mentioned.

Other than that, out of spec or worn pins/holes.

[Dustbuster]

I can see guys doing that, not here, new rifles,both triggers factory installed.
I guess the built on Monday or Friday concept works in the AR lower category....


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[Dolomite_supafly]

Picture looking down inside the FCG?

[Dustbuster]

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[Dustbuster]

It's a hiperfire 24e trigger, uses their pins..


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[LawEnforcementSalesTN]

Tactical Innovations makes a screw head pin set.. it's nice for oversize/improperly machined/out of tolerance receivers.  I use to run them on a lot of my shorty full autos - especialy the 9MMs ... they're brutal on the pins.. Only downside is their OD is slightly larger - kit comes with a drill bit... so as Yoda said.. "One you start down the dark path, forever will dominate your destiny".  I do like the cleaner look of the screws though over the KNS (just personal preference) but the KNS do work and are more importantly reversable should you want to pull them out ..

 

The pins are not suppose to rotate either, that's what causes your wear and damge when they do.

[Slpeod]

Looks like on your hipperfire the hammer spring is correct.  I've seen a lot of them reversed, just make sure it hugs the notch on the hammer and the spring legs come off to the front.

 

I would also second what LawEnforcementSales said- the Tactical Inovations or the JP Anti walk pins are personally preferred to the KNS. Half the price of KNS also without the bar running between them: http://www.brownells.com/rifle-parts/triggers-bottom-metals/hammer-parts/hammer-pins/ar-15-anti-walk-pins-prod7589.aspx?avs|Manufacturer_1=J%20P%20ENTERPRISES