Barrel slowing down?

[rhovee]

I have done a lot of research to no avail. I have a 6.5wsm and have about 500 rounds down the rifle. I have tested powder in 70-30 degrees weather and have got about 11fps swing. Rounds that have shot 3075-3070 in 43 degree weather in the past are now shooting 3030 average. Any idea why a barrel would slow down? All same lot components. My log shows fall weather being the same.
6.5 wsm
147 eldm
Fed215
RL26
Norma brass with .294 bushing

 

[rijndael]

Was your chrono data with virgin or fire formed brass?

 

[ballisticdaddy]

Was the powder loaded from the same lot? I have experienced noticeable changes but in different lots.

 

[Ringostar]

Crono set up and temp difference could give you that also. Crono's aren't always accurate either.

 

[dmoran]

It is common for me to see small amounts of velocity decay in barrels do to wear and erosion factors over there life span. But are you confident that your load used has remained 100% spot on the same? Where to say, any component variation or Lot change to primers, powder, bullets, or brass can effect a loads velocity average.
Donovan

 

[DT]

It is common for me to see small amounts of velocity decay in barrels do to wear and erosion factors in there life span. But are you confident that your load used has remained 100% spot on the same? Where to say, any component variation or Lot change to primers, powder, bullets, or brass can effect a loads velocity average.
Donovan

How about seating depth? After 500 rounds throat may have moved enough to cause that amount of velocity loss if you're not keeping up.

 

[rhovee]

Same powder, brass, bullets, powder. Only thing I messed up on is having brass with different amount of firings mixed together. My powder node from before was 60.3-61 shot 3070-3080. It now hovers around 3020-3030. Might need to order up a new barrel...

 

[dmoran]

@DT
I agree; seating in relation to throat advancement, most definitely can effect velocity.
Donovan

 

[rhovee]

I agree. I have been having the lands and they have stayed put for a bit. I had to add almost a full grain or powder to jump back up to 3070. Hoping that doesn’t put me over the top in the summer.

 

[DT]

I agree. I have been having the lands and they have stayed put for a bit. I had to add almost a full grain or powder to jump back up to 3070. Hoping that doesn’t put me over the top in the summer.

Do you mean that after adding powder you are now back to 3070? How did the accuracy hold up at the lower velocity? With that heavy a bullet for caliber in a 6.5 the 50 fps at 3020 won't mean enough of a elevation adjustment to be overly concerned with if the accuracy is still there.

 

[Hanbleceya]

How about seating depth? After 500 rounds throat may have moved enough to cause that amount of velocity loss if you're not keeping up.

Likely

 

[Hanbleceya]

I agree. I have been having the lands and they have stayed put for a bit. I had to add almost a full grain or powder to jump back up to 3070. Hoping that doesn’t put me over the top in the summer.

Heavy copper?

 

[Hanbleceya]

Was the powder loaded from the same lot? I have experienced noticeable changes but in different lots.

same chrono position?

 

[daniel brothers]

I wonder like Hanble.... Heavy Copper?

 

[rhovee]

I was also thinking heavy copper might be adding to it. Has anyone else seen this before? I did my normal cleaning with bore tech eliminator. Couple wet patches. Nylon brush wish 20 passes and pushes out patches tell clean. I did notice lots of copper on the rifling towards the muzzle. It was only 100 rounds since my last cleaning. It’s a magneto speed chrono always in the same place. I always thought that heavy copper would make bore diameter less and cause higher velocity. It was shooting .3s. It’s now shooting .5. I am mainly worried cause the es has gone from 11 originally to 40 now.

 

[Twoboxer]

Were it me, I'd remeasure and adjust distance to the lands, then add powder as necessary to get the velocity back.

If you get the SD and/or accuracy back you'll at least begin to have answers.

 

[daniel brothers]

If it were me... I'd stop everything until I got the barrel squeaky clean of all copper, powder and carbon.

 

[Gene Beggs]

What is the rifle used for? If it's a hunting rifle, you are getting good results.
Throw that chronograph away or give it to someone you want to see drive themselves crazy over trivia and just enjoy shooting your rifle. It's not a benchrest rifle.

 

[savageshooter86]

My last 284 barrel slowed down at about 350 rds. Powder charges running 2815 to 2840 were now running 2775 2805. Then my charge weights were right spot on where most said I’d end up. Prior to I was about a grain lower

 

[hunter686]

I doubt it's fouling. Fouling will speed it up not slow it down. Just gained about 25fps on my barrel untill I cleaned it and she' dropped back to the sweet spot. Accuracy when from .3 to 3/4. I'd check the lands. If you go - say for instance - jam to say 20tho jump due to errosion that could take you out your node. Especially if you are on the edge of it. That would account for your velocity, the groups opening up and the SDs being poor.

Clean your barrel, check your lands load up a new batch and go from there.