Proof barrel slowing down.

Rhovee

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I have about 400 rounds down a 30/28 nosler and the accuracy node has slowed down about 60 FPS. I use to run 3100 all day long. Suddenly she dropped off. When barrels slow down does this usually mean there close to being done?
 

Rick Richard

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If all other factors have remained the same such as same powder/lot and etc, then it is an indication it is on the downhill side. Has accuracy also diminished?
 

Rhovee

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Accuracy is decent. Still need to check it at 600 and see where it’s at. At 100 I got it to shoot about 1/2” today. But seems like I need to adjust powder charge every time I go out.
 

Rhovee

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The lands have moved .009 in 400 rounds. I check every hundred. I have kept seating depth the same. But larger bore diameter for a short distance would make sense.
 

Edd

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I have about 400 rounds down a 30/28 nosler and the accuracy node has slowed down about 60 FPS. I use to run 3100 all day long. Suddenly she dropped off. When barrels slow down does this usually mean there close to being done?
What bullet are you using?
 

odoylerules

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The lands have moved .009 in 400 rounds. I check every hundred. I have kept seating depth the same. But larger bore diameter for a short distance would make sense.
Have you kept the depth the same? Or chased the lands (moved the bullet out) as they’ve worn down?
 

Rhovee

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Sure have. I use to pressure out at about 3150 at 87 grains. 85.7-86.4 was 3100 +- 7 FPS. Now I have .7 grains and covers 3045. And pressure out at 3100. Man I really hope this barrel didn’t go south at 400 rounds. I would shoot 3-4 rounds and let it cool tell it was just a little warm. All shooting was done 60 degrees or less so the barrel cooled pretty fast. I need to find someone with a bore scope that lives in western wa.
 

Edd

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I think, based on the provided data, you are describing a barrel that is getting smoother. It doesn't mean it is worn out, it just means the lands and grooves are getting smoother and the friction between the barrel and the bullet is increasing.
 

Rhovee

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I have tried to understand that. Someone else mentioned copper fouling. But I did recently clean it. If friction is increasing wouldn’t it make the bullet and pressure faster. Like when a new barrel gets broken in and speeds up.
 

Edd

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I have tried to understand that. Someone else mentioned copper fouling. But I did recently clean it. If friction is increasing wouldn’t it make the bullet and pressure faster. Like when a new barrel gets broken in and speeds up.

I don't think a new barrel speeds up because the friction increased. I think it speeds up because the friction decreased.

If the bore surface of a new barrel is rough there will be increased friction because the bore is biting the bullet. As this biting surface wears smooth the friction is decreased and the bullet speeds up. Then as the barrel continues to wear, the area of the smooth surface becomes larger. The larger surface causes more friction.
 

Rhovee

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It’s a carbon barrel. I just cleaned it about 30 rounds ago, but was wondering if I should clean the hell out of it and maybe some excessive copper. I did notice it slowed down after I cleaned it last time. I just purchased a Lyman bore scope so I will look down it and see what’s going on.
 
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