Proof barrel slowing down.

CA48

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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.

Did you change to a different lot# of powder?
 

Rhovee

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No. All that stuff had stayed the same. I have a bore scope coming Monday. I am going to clean it really good tomorrow and scope it out and see what’s going on.
 

Rent Outdoor Gear

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If the throat has only moved .009", then you are a long way from having it shot out. I'd get worried when it gets to about .060" and slows 100 - 150 fps with the original load, and most importantly it won't group no matter what you do.
 

coyotezapper

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Seat the bullet .010" longer and retest.

You mentioned that the accuracy was just ok. If after seating the bullet out longer and it doesn't change things increase your powder charge to get velocity back to original speed.

Copper fouling actually creates higher pressure and higher pressure results in higher velocity. Its not a copper fouling problem.

The barrel is not shot out after 400 rounds on a 300/28N.

A good solid powder node will allow you to not have to chase the lands as much as a narrow powder node does. By the sounds of what you are saying the powder node is very narrow and therefore sensitive to every little change.

You may also want to polish the throat every 200-300 rounds to extend throat life. .009" throat wear after 400 rounds is actually very little wear IMO.

Keep us posted.
 

Rhovee

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I will keep you posted. I cleaned it very well and there was quite a bit of copper in there. The powder charge node is large. 1 grain is almost no change of FPS. It has moved from 3100 to 3045. It’s with a labradar so I trust the numbers. Got a bore scope coming today. I will post my results. I hate it when you search a forum for a similar topic only to find the original poster never came back to post his outcome. I also have 12 rounds loaded up to check speeds and accuracy since it’s cleaned and copper remover was used until streaking stopped.
 

lsoccorsi

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Feb 6, 2015
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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?
Typically when breaking in a new barrel this exercise is a shoot and clean process that helps smooth the lands and grooves to reduce friction and ultimately reduce copper fouling. If this process is done correctly using the proper solvents/barrel polish, it usually takes between 25 and 50 rounds depending on the quality of the barrel. If you start off with a quality barrel that was honed prior to installation, normally you don't have much of a "break in" period. If the throat has 0.009" erosion, seating the bullet out a little further will take care of this issue and is a simple fix. With respect to the slower velocity, I would try cleaning the barrel with Bore Tech Eliminator and/or KG-12 copper removal and never use a brush just the properly fitted jag. If you have a small area in your barrel that is peeling a little jacket material off the bullet, you could be loosing pressure as a result of the removal of jacket material and getting some gas blow by between the bullet & the rifling. However, this usually effects accuracy to some varying degree from small changes in group size to significant differences in group size depending on the degree of the fouling area. Also, check your powder as some powders can change from lot to lot. Best advise is to thoroughly clean the barrel will copper solvent and a jag no brushes and reduce the amount of rounds through the barrel between cleaning. See if that helps.
 

Rhovee

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I use Bore Teck eliminator and there copper only solvent. I did use a nylon brush 2 times during the cleaning process. Mostly patches with solvent. It took quite a few. As in about 30. Soaked patches before it came out streak free.
 

RegionRat

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Nov 11, 2012
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Redondo Beach, CA
If the bore scope was available before you cleaned, it may have shown a reason why. For example, maybe a rough land cut in the throat that moved on you as you shot.

If that was the case, hopefully it is now more stabilized and you will get down to more normal operations.

On cases like this, I don't hesitate to use a felt cleaning wad with JB+Kano to remove the copper and get down to a clean bbl. It can take some work to get rid of a burr in the wrong spot, but when it is gone that copper loading goes down immediately.

I would take a good look now, and after shooting, then evaluate again after cleaning, regardless of the outcome.

In for the range report, got my fingers crossed.
 

Rhovee

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Not really sure what to look for. I know some fire cracking is to be expected for 400 rounds. Going to the range now.
 

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