Cam Pin/Upper receiver wear

[styeandle]

hi guys. first post on this forum. got some unusual wear on my cam pin, and inside the upper receiver. possible causes? solutions? any help is appreciated. rifle is a stag model 8. its a carbine length piston system on a 16" barrel typically fed xm193 and xm855.

http://i1300.photobucket.com/albums/ag99/Sean_Yeandle/IMG_20130525_151401_720_zps544a0936.jpg?t=1369524899

http://i1300.photobucket.com/albums/ag99/Sean_Yeandle/IMG_20130527_081204_805_zps6688c342.jpg?t=1369667890

http://i1300.photobucket.com/albums/ag99/Sean_Yeandle/IMG_20130526_192656_865_zps78b499d6.jpg?t=1369622663

http://i1300.photobucket.com/albums/ag99/Sean_Yeandle/IMG_20130526_192928_333_zps684c337e.jpg?t=1369622650

http://i1300.photobucket.com/albums/ag99/Sean_Yeandle/IMG_20130527_080145_228_zpse92ee22a.jpg?t=1369666941

[saddlerocker]

Totally normal.
They all look similar to that

[styeandle]

Totally normal.
They all look similar to that

The chipping at 3 and 9 o clock around the firing pin hole on the can pin is normal? After only 300 rounds?

[afroney]

Not sure about the chipping at the hole, but the wear inside the ipper receiver is normal. Tapers off after awhile.

[saddlerocker]

The chipping at 3 and 9 o clock around the firing pin hole on the can pin is normal? After only 300 rounds?

I didnt see that originally on my phone.
If it is chipping then that seems abnormal, but it may have just been machined poorly from the start.

[styeandle]

I didnt see that originally on my phone.
If it is chipping then that seems abnormal, but it may have just been machined poorly from the start.

No, wasn't always there, its def chips or wear marks, not machined and they are more at like a 230 and 830 position, but opposite on the other side. As in it seems to be rubbing along the firing pin while the bolt is camming backwards. And the wear on the receiver I've seen, but thanks for the reassurance. Its that pin that's got me puzzled. Too much carrier tilt? Pin not heat treated? Just way over gassed? I dunno...

[Iraqgunz]

I am sure it is overgassed. Stags always have been as far as I recall, plus most piston AR's need an enlarged port to cycle reliably.


No, wasn't always there, its def chips or wear marks, not machined and they are more at like a 230 and 830 position, but opposite on the other side. As in it seems to be rubbing along the firing pin while the bolt is camming backwards. And the wear on the receiver I've seen, but thanks for the reassurance. Its that pin that's got me puzzled. Too much carrier tilt? Pin not heat treated? Just way over gassed? I dunno...

[interfan]

hi guys. first post on this forum. got some unusual wear on my cam pin, and inside the upper receiver. possible causes? solutions? any help is appreciated. rifle is a stag model 8. its a carbine length piston system on a 16" barrel typically fed xm193 and xm855.



Piston gun. Carrier tilt or wobble?

[Thomas M-4]

The wear points look normal I would refere back to Iraqgunz it's most likely over gased causing the wear to happen at a slightly accelerated rate.

[SpankMonkey]

IG is correct that gun is way over gassed. Check your firing pin for damage. It should be OK but that cam pin is really torquing. Expect it to fail soon. It may last a long time but I would not bet on it.

Use more oil, it will help slow the wear down some and get a stronger buffer spring.

[justin_247]

Many of the piston uppers have this problem. Just look at the reviews for Adams Arms, and you'll see all kinds of discussions about this very issue.

[styeandle]

Thanks guys! I've got an h2 buffer in it, and a stronger spring on the way, and I cover it in wheel bearing grease, but I'll use a little more to help out. Will a cam pin with a fancy coating or one made of stainless steel etc help? Or will that just wear the firing pin instead?

[sinlessorrow]

Thanks guys! I've got an h2 buffer in it, and a stronger spring on the way, and I cover it in wheel bearing grease, but I'll use a little more to help out. Will a cam pin with a fancy coating or one made of stainless steel etc help? Or will that just wear the firing pin instead?

The cam pin wear looked normal.

[AKDoug]

The cam pin wear looked normal.
Those chips around the firing pin hole don't.

[sinlessorrow]

Those chips around the firing pin hole don't.

Totally didnt see that! I thought he was worried about the finish wear on it. Looks like it was made of pot metal.

[crcjk]

hi guys. first post on this forum. got some unusual wear on my cam pin, and inside the upper receiver. possible causes? solutions? any help is appreciated. rifle is a stag model 8. its a carbine length piston system on a 16" barrel typically fed xm193 and xm855.

http://i1300.photobucket.com/albums/ag99/Sean_Yeandle/IMG_20130525_151401_720_zps544a0936.jpg?t=1369524899

http://i1300.photobucket.com/albums/ag99/Sean_Yeandle/IMG_20130527_081204_805_zps6688c342.jpg?t=1369667890

http://i1300.photobucket.com/albums/ag99/Sean_Yeandle/IMG_20130526_192656_865_zps78b499d6.jpg?t=1369622663

http://i1300.photobucket.com/albums/ag99/Sean_Yeandle/IMG_20130526_192928_333_zps684c337e.jpg?t=1369622650

http://i1300.photobucket.com/albums/ag99/Sean_Yeandle/IMG_20130527_080145_228_zpse92ee22a.jpg?t=1369666941

I had two can pins in my Stag fail. I replaced with BCM can pin and haven't had an issue since

Sent from my Etch a Sketch

[styeandle]

I had two can pins in my Stag fail. I replaced with BCM can pin and haven't had an issue since

Sent from my Etch a Sketch

thats probably what ill end up doing. im looking at LWRCI's REPR pin with the rounded top. that will fit wont it? even though its a 7.62?

[foxtrotx1]

thats probably what ill end up doing. im looking at LWRCI's REPR pin with the rounded top. that will fit wont it? even though its a 7.62?

No reason to deviate from the tried and true. A normal cam pin from a decent manufacturer works great.

If the upper is as over gassed as suspected, an H3 may serve you well.

[styeandle]

I'm using an H2 already haha. And OK, just got a reg pin with a NiB coating, so hopefully that'll do the trick. Thanks guys