Gouge inside upper

AR/M4 AR General Discussion
1

I just received a used LMT MRP Rifle upper (swapped my CQB).

When I received it today I found a gouge opposite the ejection port. I know this isn’t normal wear and the guy said its possible he did it when he was trying to get a 6.8 barrel in battery (said he didn’t notice it before he sent it).

I’m not to concerned about aesthetics, I just want to make sure this won’t interfere with any of the guns operation at all. I plan to turn this into a SPR type build and want to be sure all is good.

Am I good to go?

2

Is this a Piston upper?

3

nah its a rifle length upper, don’t think you can use piston setups in the rifle length.

4

It almost looks lke the cam pin recess is out of time with the face of the barrel extension.

5

I would contact LMT. It looks more than normal wear. I’m sure they would help you out.

6

If the gouge was not disclosed prior to the trade, I would not be happy with that.

7

Was not disclosed prior to trade.

Would contacting LMT help? I don’t think it would be under warranty.

8

IME, LMT will help you regardless. They should at least be able to tell you what’s going on and if it’s even a problem.

9

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10

That is not normal wear, take a look at how uneven the gouge/cut/ grinding is. It almost looks intentional, or like it was done while someone was using tools the wrong way.

11

define normal? i’ve seen plenty of uppers like this and many not, but because i’ve seen enough of them like this and by running a simple bell graph it indicates that this is within the normal wear in this area. i’ve seen this mostly in direct impingement systems. ymmv

12

The guy made it sound like he thought it was done when he was “trying to get it to get loose”. Assuming he put a tool down there to try wiggle it out.

13

Consult LMT either way. it doesn’t look intentional or accidental, but rather wear from the cam pin. Email them a pic and I’m sure they’ll get back to you regardless of ownership status.

14

I am going out on a limb here. Bear with me. It looks to me (SWAG) that the previous owner inserted the BCG into the upper and the firing pin wasn’t installed. He then dicked around and the bolt cam pin rotated and got jammed in the upper.

He then dicked about with something until it came out. If that didn’t happen then there is something else going on because that gouge is pretty deep and doesn’t appear to be from “wear”.

15

I’m relatively new to ARs. What is the function of that notch?

Here’s a picture of mine with what I assume is normal wear:

16

It is the recess where the cam pin sits when the gun is in battery.

17

FYI, This is biased on nothing more than my opinion…

It looks to me like that was caused by a broken bolt freezing the cam in place during firing. Under recoil, the whole thing would of locked up tighter than a tick. When the shooter could not clear the malfunction with “SPORTS” they freaked out and used something like an ammo can and a GI cleaning rod section to hammer it out.

Its likely that they then replaced the broken parts with cheap stuff they got from some board EE but they still had lingering doubts about the upper failing again and decided to trade it off at a gun show or EE to someone else to deal with…

The only thing I am surprised about is that the bright spots were not blackened with a sharpee marker, prior to being traded to the new unsuspecting owner…

Again, this is just a WAG on my part and I have no actual knowledge of the events or the parties involved…

S/F

B

18

normal wear, it seems would just be the finish worn off, I’ve seen several instances of this but actual displacement of metal seems abnormal.

19

For anyone claiming this is normal wear, please post a few images of the various weapons you work with which show the same uneven damage.

20

Good call. Quite possible.