Lost 100 fps after 550 rounds

[Mc Fraser]

Hello,
I have a carbon barrel that lost about 100 fps after less than 600 rounds. I looked at my order history, I have 400 bullets ordered, 100 that a buddy bought for me and 80 factory loads. I would appreciate some thoughts on the matter.
I went to the gun range two weeks ago and noticed that I'm low at 550 yds. I went back over the weekend with my labradar, and MV went from 2975 to 2877 I shot 50 rounds after a good cleaning.

History:

• 300 PRC, 78.9gr N570 not even close to max pressure, Hammer Hunter, defiance action, premium carbon wrapped barrel.
• I got the rifle 2 years ago from the smith, didn't have time to do load development, bought 4 boxes of Hornady factory ammo, broke in the barrel, 15 shots cleaned after 3rd, and then cleaned after every 10th. I did that for 3 boxes, and kept one for hunting. I did not have a Chrono. Shot a cow elk at 800 yds and a deer at 400.
• After the hunting season ended, we started load development and did a ladder test with H1000, Retumbo, and N570 - 50 bullets were used to find a velocity node. Found 2975fps to be consistent with N570 and 214HH.
• Moved to depth seating with N570, and another 100 bullets went down the barrel.
• Everything up to 550 ish was used for practice.
• I should mention that my ES is 3 and SD 1.4 on a 5-shot average.
• Equipment used: Redding type S dies, Forester press, AutoTrickler with FX120, the list goes on, but I pretty much have premium tools.
• Cleaning: Carbon rod, bore paste, usual cleaning supplies like first choice (pretty much what competition shooters use). The cleaning performance is checked with a borescope. I never used brass brushes, only nylon.
• Observations:
  • My first thought was the FX120i. I have yet to verify the load against another scale, but I reload for 2 other rifles, and their velocity has not changed.
  • I have not changed my reloading process, but I have not excluded me factor.
  • The Labradar I used over the weekend that yielded 2877 fps, was different from the one I used for load development.
  • The rifle still shoots well, 1/4 MOA at 100 and consistent 2 inch groups at 550 yds. I have access to another range that goes 900 yds, last time when I was there I shot 3 in groups. I have access again next week.
  • I am planning to take the rifle to my Smith, I checked the barrel and it looks fine but he has decades of experience.

Thank you in advance for your thoughts.

 

[marksman1941]

Any temperature change between load testing and the most recent shooting session?

 

[Beluebow]

Did you use an abrasive to clean your barrel?

 

[Calvin45]

Any temperature change between load testing and the most recent shooting session?

Number one suspect for sure.

 

[Calvin45]

Second thought…they do say n570 is a throat eater like no other. Perhaps you've created some "freebore" at this point that's dropping velocity with equal charge weights.

 

[Coyote Shadow Tracker]

Hello,
I have a carbon barrel that lost about 100 fps after less than 600 rounds. I looked at my order history, I have 400 bullets ordered, 100 that a buddy bought for me and 80 factory loads. I would appreciate some thoughts on the matter.
I went to the gun range two weeks ago and noticed that I'm low at 550 yds. I went back over the weekend with my labradar, and MV went from 2975 to 2877 I shot 50 rounds after a good cleaning.

History:

• 300 PRC, 78.9gr N570 not even close to max pressure, Hammer Hunter, defiance action, premium carbon wrapped barrel.
• I got the rifle 2 years ago from the smith, didn't have time to do load development, bought 4 boxes of Hornady factory ammo, broke in the barrel, 15 shots cleaned after 3rd, and then cleaned after every 10th. I did that for 3 boxes, and kept one for hunting. I did not have a Chrono. Shot a cow elk at 800 yds and a deer at 400.
• After the hunting season ended, we started load development and did a ladder test with H1000, Retumbo, and N570 - 50 bullets were used to find a velocity node. Found 2975fps to be consistent with N570 and 214HH.
• Moved to depth seating with N570, and another 100 bullets went down the barrel.
• Everything up to 550 ish was used for practice.
• I should mention that my ES is 3 and SD 1.4 on a 5-shot average.
• Equipment used: Redding type S dies, Forester press, AutoTrickler with FX120, the list goes on, but I pretty much have premium tools.
• Cleaning: Carbon rod, bore paste, usual cleaning supplies like first choice (pretty much what competition shooters use). The cleaning performance is checked with a borescope. I never used brass brushes, only nylon.
• Observations:
  • My first thought was the FX120i. I have yet to verify the load against another scale, but I reload for 2 other rifles, and their velocity has not changed.
  • I have not changed my reloading process, but I have not excluded me factor.
  • The Labradar I used over the weekend that yielded 2877 fps, was different from the one I used for load development.
  • The rifle still shoots well, 1/4 MOA at 100 and consistent 2 inch groups at 550 yds. I have access to another range that goes 900 yds, last time when I was there I shot 3 in groups. I have access again next week.
  • I am planning to take the rifle to my Smith, I checked the barrel and it looks fine but he has decades of experience.

Thank you in advance for your thoughts.

The shooter next to you "Stole" some of your ammo.

 

[hesse]

I would say temp to start . The other thing is can you get the original chronograph. I would not be surprised if the is a difference between the two also

 

[Critter Picker]

Are you using powder from same lot?

I've seen lot to lot variations greater than that.

 

[MagnumManiac]

Your throat has eroded enough to drop velocity, it's normal.
To get the velocity back, you need to add powder, not chase the lands.
My barrels for F-class do this throughout a season about 3-4 times and at the 6 month mark may get a setback and re-chamber depending on the amount of haze cracking.

Cheers.

 

[Huntnful]

N570 ate it up. Just add powder, and you'll continue to have to add powder throughout the rest of the barrel life. It's not a one and done fix. It'll continue to erode and lose pressure, and you'll have to continue to add powder. N570 is vicious

 

[Kimber7man]

You're using bore paste every time you clean the bore? JB bore paste or??
I'd suspect that may have helped accelerate the throat erosion.

 

[MTGEEZER]

N570 ate it up. Just add powder, and you'll continue to have to add powder throughout the rest of the barrel life. It's not a one and done fix. It'll continue to erode and lose pressure, and you'll have to continue to add powder. N570 is vicious

This thread has me thinking. Tikka 6.5 PRC, 1 in 8 twist, was running 60 grains RL26 behind 124 Hammer Hunter at 3365 FPS, 1.6 inch groups @ 200 yards ( our range only goes to 200 ). Lost accuracy and 40-50 FPS late in summer so cleaned to bare metal, bore scoped and found very significant fire cracking in throat @ 350 rounds through barrel. Is RL26 hot or abrasive enough to do this? HELP!

 

[MagnumManiac]

Double base powders in that heat range are throat burners. A single base is kinder, but it depends on kernel size, short cut powders are less abrasive, the Extreme line are kind on barrels…

Cheers.

 

[Barehandlineman11]

Good ol n570 like sand blasting the throat with a torche. Gets that speed though