Unusual wear in my Upper?

[Uncontested]

Hello, so I recently purchased a Core15 TAC M4 Piston Rifle, after putting some rounds through it I've noticed an unusual wear spot in the upper receiver. I've included a picture. Can anyone tell me what might be causing this, or if this is 'normal' will it be a problem? I thought it might have been the BCG but I didn't see any sort of wear that matched what you see in the picture.

This is my first personally owned AR style rifle but I don't recall seeing anything like this when I was in the military.

http://img22.imageshack.us/img22/858/20130101085849.jpg

Thanks.

[eternal24k]

It's from the cam, normal as far as I am concerned, almost all of my rifles have it, notably my SBRs. Maybe pistons and SBRs show more due to the more violent cycling, maybe not. I would not worry about it.

[KrampusArms]

It looks like the usual wear from the cam pin, but elongated, & more severe. I have two AR uppers that have wear similar to that, but not as pronounced.

Whats your round count?

I say keep shooting it, I have a feeling its self limiting. My guess is that the worst of it is over.

[michael word]

I have the same wear in both of my ARs, although not as bad. could be due to the more violent action of the piston system.

[Uncontested]

It looks like the usual wear from the cam pin, but elongated, & more severe. I have two AR uppers that have wear similar to that, but not as pronounced.

Whats your round count?

I say keep shooting it, I have a feeling its self limiting. My guess is that the worst of it is over.

I've only put 240 rounds through it so far. Hopefully it is just normal wear and tear, don't wanna have to send it off already.

Thanks for the replies so far, feel a lot more at ease about it. The main thing that had me worried was finding all the metal shavings lol. Now that I look closer at the cam pin I can see where its hitting and the finish is worn off.

[gan1hck]

looks like mine

[KrampusArms]

I've only put 240 rounds through it so far. Hopefully it is just normal wear and tear, don't wanna have to send it off already.

Thanks for the replies so far, feel a lot more at ease about it. The main thing that had me worried was finding all the metal shavings lol. Now that I look closer at the cam pin I can see where its hitting and the finish is worn off.

Hey man
Here's my opinion.

Don't send it off just yet. Fire the rifle 200 more times. If the wear stays the same, (Which I'm willing to bet it will) keep the rifle.

Also consider, how is your rifle performing? Is it reliable & accurate so far? Do you like it? It's easy to get hung up on stuff like this, as we pay precious $$$ on this stuff, & we want it to be perfect. I'm guilty of being concerned over my equipment too.

At the end of the day, we must remember that these weapons are machines. They are literally trying to tear themselves apart. It's the nature of the beast.

Your weapon is also a piston driven rifle which will be subject to wear in a different way in certain areas. I say shoot on, I think your rifles fine.

[Eric D.]

That's normal. Here's why it happens: When a round is stripped from the magazine and pushed into the chamber there is a reaction force trying to push the bolt into the carrier. Of course, the bolt can't be pushed into the carrier without rotating. The cam pin riding in the track of the of upper is what prevents the bolt from rotating until it gets to the relief cutout where it rounds over that sharp corner. I remember reading one of Colt's possible improvements was adding a steel strike plate in that area to prevent that wear you see.

[Sparky5019]

As said above, normal wear from cam pin. If it bothers you you can gently radius and polish the square corners on that out side of the cam pin. Did that on mine when I first noticed the mark and the wear stopped in that area. This is one of the reasons behind POF's roller cam pin but a much cheaper and easier solution.

I'll try to post a pic when I get home in a bit.
Sparky

[thehun]

looks like mine

[BIGUGLY]

Not sure if i remember correctly but I believe if you are really concerned about it POF makes a round cam pin to reduce this type of wear.

Correct me if I'm wrong.

[7 RING]

Initially, you will see some more pronounced wear as the rifle breaks in.

Lube it. Shoot it. Don't worry about it.

[Sparky5019]

As promised...

http://i675.photobucket.com/albums/vv117/SparkySRNA/CamPin_zpsee149461.jpg

Now if you put it in "backwards" it will wear as "normal"; the radius will stop that wear. At a much lower price than POF's kit and no need to torque and stake new gas key!

Sparky

[Skyyr]

As mentioned, normal. A Noveske I previously owned had the same wear after ~200 rounds.

If you want to avoid it entirely, upgrade to the POF roller cam pin. If not, just shoot it. It will eventually stop wearing.

[markm]

This is a non issue.