Bolt Defect in Colt LE6940 ?

[Naphtali]

I'm attaching pictures of what appears to be a new defect in the bolt of my Colt LE6940, in the hopes that someone with more armorer knowledge than me can tell whether this needs replacing or can be safely ignored.


1.jpg


2.jpg



Relevant info is as follows:

-- The rifle has not been modified during its life (other than RDS etc. attached to the quad rail).
-- It was manufactured in 2013, purchased new by me and shot only by me since then.
-- The rifle has never had any issues or malfunctions during its life.
-- I clean it well every time I shoot it and keep it properly lubed (maybe somewhat over-lubed) with G96 lubricant prior to shooting.

-- The round count 2 weeks ago was 1,500. Ammo was exclusively decent quality 5.56 (e.g. Federal and IMI M855, Federal mk318).
-- I then did a carbine course this past weekend, at the conclusion of which I noticed this defect during cleaning and inspection.
-- The defect was 100% definitely NOT present when I lubed / inspected the bolt prior to the carbine course.

-- I shot 1,200 rounds at the course. I lightly cleaned / lubed everything at the 600 rd halfway mark but didn't inspect anything then. So the defect was NOT present at 1,500 rounds, and it WAS present at 2,700 rounds.
-- Ammo shot at the course was 1,000 rds IMI M855 and 200 rds Federal 5.56 Frangible (not .223).
-- I had no issues / malfunctions during the 1,200 rounds shot during the course.
-- At the conclusion of the course, I noted this copper-colored area during cleaning and inspection of the bolt.
-- Visibly you cannot see any 3D defect or outpouching on close inspection, but if you run your fingernail over the area, you can feel it is ever-so-slightly protruding out from the original bolt contour in the copper-colored area (i.e. it catches your fingernail there).
-- The copper color cannot be cleaned off - maybe I'm seeing the color of the original metal under the black finish, and the color change is due to the black finish now being missing there?

Any thoughts on what has happened, as well as recommendations, would be most appreciated!

[26 Inf]

Not something I'd worry about.

If you look at the attached picture of a cutaway bolt carrier you can see how the gas would dump from the gas tube into the area behind the bolt's gas rings, right about where you have indicated in your picture. (the attached thumbnail is clearer - don't know how to get rid of the first one)

Attachment 56330

Remember that the bolt is rotating as the bolt cam pin follows the cut out in the bolt carrier. You can see yhe marks on the bolt's tail in the picture.

Here's an animation, start watching at about 3:05:

https://www.youtube.com/watch?time_c...&v=wAqE-KLbiYc

It's just fine.

[Naphtali]

Thank you for the helpful response / pictures and video link.

If the bolt itself isn't at risk for failure (because this area isn't subject to withstanding high gas pressure), is it possible for this slight protrusion to damage the bolt carrier interior, as it rubs along that narrowest hole inside the carrier? It might not be a problem as it currently is (the protrusion is minimal now), but whatever problem(s) took my bolt from normal to this mild failure of integrity, it seems it would take even less force to go to a greater level of integrity failure (and greater protrusion).

And if / when it's worse, wouldn't something (either the bolt or the carrier, or both) have to wear in some major way, if this part of the bolt can no longer fit properly through the carrier hole it slides in? Or if neither the bolt nor the carrier hole "broke" from wear, but the protrusion worsened to where the bolt couldn't slide well / was limited in rearward motion in the carrier at this point, would that cause a failure to operate properly (e.g. a permanent inability to fire the weapon if the carrier couldn't move forward enough on the bolt, and was always held back by that protrusion slightly out of battery when a round is manually chambered)?

This is purely a training rifle, so if this problem's worsening still poses no danger, then I'm happy to run it even if it fails. But I'd hate to ruin the carrier over time, if replacing the bolt now would prevent future damage to the interior of the carrier. I'm assuming the copper color is where the interior of the carrier has already worn off the bolt finish at this protrusion... what I cannot possibly see is whether / how much the carrier interior hole is similarly worn by this protrusion.

[498cm3]

It looks like a tiny piece of bullet jacket or casing deposits fused to the bolt. Scrape it off with your pocketknife.

Sent from my XT1031 using Tapatalk

[Naphtali]

It looks like a tiny piece of bullet jacket or casing deposits fused to the bolt. Scrape it off with your pocketknife.

Sent from my XT1031 using Tapatalk

You hit the nail on the head. I had no idea copper shavings could fuse to the bolt, but a dental pick scraped off the copper deposit, and the bolt is back to normal. Thank you!!!

[498cm3]

You hit the nail on the head. I had no idea copper shavings could fuse to the bolt, but a dental pick scraped off the copper deposit, and the bolt is back to normal. Thank you!!!

Glad I could help.
Best wishes.

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