AR-15 Trigger Pin Drift?

[DoubleTapDrew]

I'm having an issue with my Oly AR-15. When firing, the pin that holds the trigger assembly to the receiver starts to drift to the right. After about 45 rounds, it goes far enough that it is no longer in the hole on the left side of the receiver and the pin shifts a little inside the receiver so it's no longer lined up with the hole. The gun will keep firing, but as you can imagine, the trigger pull gets pretty bad since the whole assembly can now pivot inside the receiver.
Has anyone else encountered this issue with an AR? I imagine it's just poor fitting from the factory and the solution would be to flare out the left end of the pin (it always drifts from left to right if looking down on the gun from above). Does this sound right? I've never flared out the end of a pin before and I'd hate to bend the sucker, so is there any special technique to this or do I just start smacking it with a hammer?
Thanks for any advice!

 

[rbernie]

According to my local gunsmith (the one I trust), Olys are known for this sort of problem. You can swage up the pin ends a bit or install anti-walk pins. I'd recommend the anti-walk pins as the more permanent and elegant solution.

 

[BobCat]

Before you start beating on it, look for the groove that the spring is supposed to ride in, and make sure it is on the proper side, and engaged. Remember that the receiver is aluminum and you can crack it if you get too enthusiastic with the hammer.

I'm the wrong guy to answer your question; someone here who knows more about AR-15s will give you a fuller, more likely to be correct, answer. My ARs have aftermarket two-stage triggers so I'm not as familiar as I should be with the stock setup - but there are grooves in the trigger and hammer pins, that the springs are supposed to engage, to keep the pins from "walking" side to side.

Bushmaster also sells "anti-walk" pins, which are a little longer than stock and have a groove for a c-clip on each end; c-clip and groove on the external wall of the receiver. I'm told they are not "legal" for Highpower matches because they alter the external appearance, but if you do not shoot Highpower, who cares?

I hope this helps.

Regards,
Andrew

EDIT: Again, I type too slow.

 

[DnPRK]

http://www.brownells.com/aspx/ns/store/ProductDetail.aspx?p=13801&title=AR-15+HAMMER+&+TRIGGER+PINS

 

[DoubleTapDrew]

Oh, I didn't know that the pins have grooves for the springs. I'll try to find them. I'm not super-familiar with AR's yet but I'm learning.
I might try those anti-walk pins if all else fails. Do the c-clips go on the outside of the reciever? I won't ever shoot this rifle in highpower (it's just a 16" plinker) but I've been toying with the idea of building an AR for such when I learn more about them.

 

[Bartholomew Roberts]

Usually on a stock AR15, the trigger pin only walks if the springs are installed incorrectly. There is a groove in the pin that the end of the spring fits into and the tension will hold the pin in fine.

Occasionally when something is really screwed up with the parts, you will still have the pin walk; but more often the spring is just installed correctly.

 

[2TransAms]

On my RRA,previous owner Bubba did a trigger job and wallowed out the holes.The pin would walk out and even cracked once. I bought a new one at the gun show,wrapped the ends with plumbers tape and wedged the pin in place. Works fine so far except that I expect I will need new tape every time I take it apart.In other words,it's probably not a good permanent solution.

 

[MisterPX]

THe trigger/hammer pins should have a couple grooves in them, one in hte middle, and one towards the end of the pin. Make sure the hammer spring tail rests in the outer groove on the trig. pin.

 

[Onmilo]

If this helps, the groove on the trigger pin goes to the magazine release side of the receiver.

 

[444]

Do not buy any of those pins with the external e-clips. They stick way out and you WILL gouge your skin with them. And, they look like crap.
The only way to go is the KNS pins. They work, they look good, and FWIW they allow you to apply oil to the hammer and trigger from inside the pin.
These are very popular with full auto lowers.

I have an SGW (now Olympic Arms) lower and the pins walked on it. I replaced them with KNS pins. I now have KNS pins on everything, not because they are needed but because I like to accessorize.

 

[Ironballs]

my first bushie walked on me,.. since then, every ar gets antiwalk pins

 

[Thin Black Line]

You noted this was a "factory" rifle. I've seen a lot of slap-togethers at
the g-shows that were being sold as name-brand rifles using both off
brand parts kits and used GI parts as "new." The only thing new was
usually the receiver......just a thought to file under "buyer beware."

 

[BillL223]

I've shot about 10,000 rounds through ARs with JP anti-walk pins. No gouges, no problems.

 

[DoubleTapDrew]

Thanks for the tips. This is a factory Oly. A K4 series but I have no idea if it's been disassembled before I owned it so I'll check out the tips others posted. I glanced in tonight and didn't see any grooves where the springs rest so when I have more time I'll pull it apart and examine it further.

 

[warmrain]

That's right Drew, The pins have to be oriented so that they are captured by the spring tails...