Bore damage around gas port?

[esaabye]

I have an 18inch white Oak 1/8 barrel with about 10-15k down the tube. I have been fighting some consistency issue, particularly with heavy rounds. Today I tore down the rifle to clean and verify all components. I noticed after cleaning the barrel that when passing a patch there is an inconsistency in pressure needed to push it past the gas port. When I looked down the bore I see what looks like a dark or non replace tube specs around the gas port.

I check several other rifles and none look like that.

questions?

anyone seen this before?
what caused it, was it a miss fitting gas block (was this self inflicted)?
I am assuming this barrel is toast, suggestions for an in stock 18 inch barrel?

[earplug]

How are the groups at 100 yards from a solid rest? A occasional flyer is not a barrel issue. Every bullet takes the same path. Have you looked at concentrically aligned projectiles?
Longer bullets are harder to seat perfectly without a fancy seating die. I use a Redding.

[esaabye]

I am seeing typical groups on the 55s, 3/4 -1 MOA I get about the same on the 77s and then I’ll get a big shift and the group opens up 3-4 MOA. I have swapped gas block to verify clearance, swapped sights, played with ammo, reseated the barrel and re-torqued. Everything I can think of.

[Oscar77]

I'm confused on what you are saying:
-You get random huge groups but then the groups shrink back down?
-Or once the barrel shot 3/4-1" groups but now it's huge?

Also......"...see what looks like a dark or non replace tube specs around the gas port......."
What does that mean?

PS if you truly have 10-15,000 on the barrel............ replace it, you got your money out of it.

[Tim K]

I'm confused on what you are saying:
-You get random huge groups but then the groups shrink back down?
-Or once the barrel shot 3/4-1" groups but now it's huge?

Also......"...see what looks like a dark or non replace tube specs around the gas port......."
What does that mean?

PS if you truly have 10-15,000 on the barrel............ replace it, you got your money out of it.

Exactly this. Every word of it.

[sportbikeco]

they do wear like you mentioned past the gas port, seen it in sectioned barrels on barrel life tests around round count you mentioned. I think a lucky Gunner vid on YouTube shows it pretty well.

[esaabye]

Spell check got me. What I am seeing in the bore is a dark or non reflective ring at the area of the gas port. From a performance perspective with 77’s the group open up after say 5-10 rounds. Meaning group 1 looks good but group 3 may not be on the target at 100. I do think round count is about right so I am ok with replacing but I was wondering specifically about the wear pattern and had anyone else seen this?

[Hoser]

Gas port erosion is starting to tear up your jackets.

Time to replace the barrel.

[Oscar77]

OP:
Ok.....
What sportco said: If you google the Lucky Gunner ammo test, they section some shot up barrels and you can see the port erosion.

Next if its a "ring" around the circumference of the barrel, then you had a stuck bullet and now your barrel might be bulged.
If the "ring" is simply around the port itself, it is worn BAD for you to see it so well.

Lastly what Hoser said, get a new barrel and move on.

[BPTactical]

Hoser nailed it.
If you look at a higher round count barrel with a borescope the gas port will look like Haley’s Comet.