Proof barrel slowing down.

[RegionRat]

What you are looking for is lots of copper fouling in the first parts of the throat and lands. Then anywhere else downstream in the bbl.

Rough spots where the lead angle is cut into the lands will cause that ogive seating depth number to change quickly and also to foul.

Any downstream rough spots that are tearing up the bullet jacket are also a contributor to excess copper fouling.

 

[Rhovee]

Here is another picture but further down the rifle. About 1.5" past the beginning of the barrel.

 

[RegionRat]

Here is another picture but further down the rifle. About 1.5" past the beginning of the barrel.

Now we have to see if any of that fire cracking zone is responsible for copper fouling after the range session.

 

[kfreeze]

How often do you clean your barrel? A lot of 28 nosler guys say they need to clean every 30 rounds to keep their accuracy good. May not be the case for the 30-28 nosler but could be worth looking into.

 

[johnlittletree]

Well 400 rounds is not much. I go at least 300-500 rounds between cleaning my F-T/R rifle. Have you slugged the bore yet or put a bore scope down it? Nitride is the friend to long bore life and hot cartridges! To have a consistent drop in velocity across the board on every shot assuming you have accounted for temp out side is significant and has to be leaving a trace in that barrel. How old is the powder could it be a factor?

 

[Rhovee]

Well I went out today and decided to give some pretty beat up Nosler brass a try. I can say it worked good. Group was at 200 and was 1/2" 3 shots. It's still slower at 3060-3062-3062. It was shot prone with atlas bipod and rear bag. But I am happy and doesn't seem shot out. Came down 2 clicks and over 1 and she should be zeroed.

 

[tim_w]

Get some jb on a tight patch and polish up just the throat be sure to stop where the cracking stops you see in the bore scope. You can use the scope from breech end and cleaning rod from muzzle to find and mark the exact spot on the barrel to stop. Work it back and forth. If you move a tight patch first and notice the feel you should notice a difference after some time with the jb. Also save some good clear image shots with the scope prior so you can see what effect the polishing is having. It may be slight visually but still noticable.