Anti-walk pins in AR lower

[Stape]

I built an XM177E2 retro AR a bit back, I shoot it occasionally and every time I do, within 100rds the hammer pin walks out and binds up my hammer being askew and all. I've oriented the pins both ways I can, but the problem persists. So, I installed a set of anti-walk pins from Rise Armament. They went in with zero difficulty, but now my hammer is sluggish, like its impeded, something is slowing it down resulting in light primer strikes. Light primer strikes are most notable on the first round after releasing the BCG on a fresh magazine, after manually cycling, I might get 2-3 light strikes resulting in a failure to fire out of 10 rounds. Problem is consistent regardless of ammo used. I don't think the anti walk pins are oversized, interfering with the hammer travel, I installed them easily with my fingers and a slave pin, didn't have to tap them into place, but it definitely doesn't move smoothly and free like it should. To be honest this is probably one of my only problems I've ever encountered of the sort.

Pertinent info: CMMG LPK, Armalite lower.

Ideas?

 

[Snora]

Pics? 20-30% FTF on a formerly working gun sounds like something isn't assembled properly. You mention it doesnt move smoothly like it should- what happens when you put the old pins back in?

 

[backinblack]

Hammer pin is designed to rotate in the receiver. Check the little spring wire in the pivot hole of the hammer to be sure that it's in place. It's what rides in the center groove of the pivot pin. One leg of the hammer spring rides in the side groove of the sear pin. The sear rotates around it's pin, and the pin is stationary. Anti-walk pins are only useful with drop-in trigger packs, else they are not necessary, IMO.

 

[Archilochus]

Pertinent info: CMMG LPK,

Ideas?

Well, of all the different brand LPK's I've installed, the only ones that have had problems have been CMMG parts. So, that's where I'd start. Do you have another FCG you can drop in?

 

[Stape]

Thanks for the info. I do have scads of other parts and complete LPK's I can try. I'll start with the orientation of components and parts, maybe I just bone-headed it and F'd up.

 

[kerryman71]

If you completely disassembled everything to put the new pins in, I'd start there. I turned my AR into a bolt action rifle once by doing that

 

[moojpg2]

hammer spring installed incorrectly?

 

[Stape]

hammer spring installed incorrectly?

I can't imagine putting it in incorrectly but now I'm gonna have to check lol

 

[pastera]

I can't imagine putting it in incorrectly but now I'm gonna have to check lol

From what I understand if your hammer pin walks the spring is in backwards

 

[Stape]

From what I understand if your hammer pin walks the spring is in backwards

What ive been reading as well. Now, I've built dozens of lowers with no problems, but not saying i'm above making a mistake. Gotta get home , break it down and see.

 

[bfm]

What ive been reading as well. Now, I've built dozens of lowers with no problems, but not saying i'm above making a mistake. Gotta get home , break it down and see.

Hammer spring holds the trigger pin in place and should work even if it is installed backwards, tough if backwards that could cause light strikes. Possible you have a the pins swapped? Though a lot of pins are universal, I have seen some that had just one groove for the hammer pin and two for the trigger.

 

[mikeboston]

hammer springs need to go over the pin

 

[backinblack]

Stock pivot pins are both identical with a groove in the center for the hammer, and a groove on one end for one of the hammer spring legs, and they are completely interchangeable in both position and orientation. I'm sure there are design exceptions with boutique pins.

 

[Uzi2]

OP, barring any assembly mistakes you may have made, have you checked to see if your receiver holes were drilled properly?