big loss in speed. what is the cause?

[fisherman983]

rifle is a 264 win mag, approx. 400-600 rounds down the barrel
I did load work up when I had the rifle built. found something it liked, and have used that same load for awhile. the last time I made ammo, it shot consistently @ 3125, I had approx 100 rounds loaded up. all from the same powder lot, same primer lot.

the groups have opened up a little bit, and im now running right at 3000 fps.
what could/would cause a loss of so much speed and accuracy, without having changed anything?
throat erosion? barrel worn out already?
the rifle was never miss treated.

 

[Trnelson]

Doesn't sound like you are pushing it too hard at all to me. One thing that comes to mind is the brass. How many times has it been fired? How often are you trimming, full-length sizing, and annealing? IMO it sounds like a release pressure issue with work hardened brass. Secondarily, this may sound silly but, when is the last time you've fully de-coppered the barrel?

I too have a couple of 264win rifles, one with similar mileage, they are my favorite long range hunting rigs in my safe. That particular rifle has 614 rounds down the pipe. Every rifle is a little different and needs different things to shoot well. That rig needs to have the copper fouling scrubbed out every 40-50 rounds or the groups open significantly and the SD goes out the window and it patterns like buckshot completely by 60 rounds. Clean out the copper fouling and it's right back to where it was previously. I'm shooting the 143 ELDX at 3,168fps with an SD of 8-9fps. Plenty of threads here and elsewhere that detail the coppering issues with the 143 ELDX at higher velocity so I won't waste your time re-hashing all that information.

When I used the 140 berger hybrids I could get about 100 rounds in between full de-copperings before accuracy started to deteriorate. I anneal my Nosler brass at every firing and trim to 0.05" less than my chamber length. I neck size for four loadings and then need to partially size and bump the shoulder back after the fifth firing or the bolt gets tough to close.

 

[Gunpoor]

That sounds like throat erosion but without a look through a bore scope that is just speculation. Did you happen to have a Douglas barrel put on this rifle?

 

[fisherman983]

That sounds like throat erosion but without a look through a bore scope that is just speculation. Did you happen to have a Douglas barrel put on this rifle?

It's a bartlein #3b. My gunsmith said it was the straightest bartlein they had seen up to that point.

 

[fisherman983]

Doesn't sound like you are pushing it too hard at all to me. One thing that comes to mind is the brass. How many times has it been fired? How often are you trimming, full-length sizing, and annealing? IMO it sounds like a release pressure issue with work hardened brass. Secondarily, this may sound silly but, when is the last time you've fully de-coppered the barrel?

I too have a couple of 264win rifles, one with similar mileage, they are my favorite long range hunting rigs in my safe. That particular rifle has 614 rounds down the pipe. Every rifle is a little different and needs different things to shoot well. That rig needs to have the copper fouling scrubbed out every 40-50 rounds or the groups open significantly and the SD goes out the window and it patterns like buckshot completely by 60 rounds. Clean out the copper fouling and it's right back to where it was previously. I'm shooting the 143 ELDX at 3,168fps with an SD of 8-9fps. Plenty of threads here and elsewhere that detail the coppering issues with the 143 ELDX at higher velocity so I won't waste your time re-hashing all that information.

When I used the 140 berger hybrids I could get about 100 rounds in between full de-copperings before accuracy started to deteriorate. I anneal my Nosler brass at every firing and trim to 0.05" less than my chamber length. I neck size for four loadings and then need to partially size and bump the shoulder back after the fifth firing or the bolt gets tough to close.

I was unaware of the issues with the 143 eld-x and coppering issues. Some brass has been fired 4 times and I did a test with some brand new never fired brass and the stuff that's on the 4th loading. Same results. I've never annealed any of my cases. And I partially neck size with a hornady die. I haven't ever fully decoppered the barrel. It's always shot great and never gave me a reason to change anything drastic.

 

[ShtrRdy]

..... to double check I understand ........ the cartridges that are giving you 3000 fps are from the same "batch" that you previously measured 3125 fps? You didn't load up another batch with the same components at some other time?

 

[fisherman983]

..... to double check I understand ........ the cartridges that are giving you 3000 fps are from the same "batch" that you previously measured 3125 fps? You didn't load up another batch with the same components at some other time?

Yea that's correct

 

[ShtrRdy]

Are you using a different chrono? Or are the lighting conditions different from the two times?

 

[fisherman983]

Are you using a different chrono? Or are the lighting conditions different from the two times?

Same chronograph
Lighting conditions may be different but my rifle range goes to 550 yards. Using my old data with the 3125 speed, im hitting low.
Adjusting my dope in my shooter app, and going with the new speed of 3000 fps, I'm dead on

 

[elkaholic]

I have not read through the entire thread so pardon me if this has been covered. Whenever I see 264 WM with a few hundred rounds through it, I have to wonder if the throat is shot out. Have you checked to see how much the coal has increased to the lands as compared to when you were getting more velocity?

 

[fisherman983]

I have not read through the entire thread so pardon me if this has been covered. Whenever I see 264 WM with a few hundred rounds through it, I have to wonder if the throat is shot out. Have you checked to see how much the coal has increased to the lands as compared to when you were getting more velocity?

Unfortunately I didn't check that when i had it built. I'm hoping I can get ahold of my Smith and maybe get some numbers to get started on that.

 

[Greyfox]

Not sure if it's the same issue but I have a 6.5x284 that I had worked up a an accurate load at 3000FPS. At 250 rounds the accuracy fell apart and I have not been able to restore it. Velocity was slightly lower. Tried every thing. Copper removal, different loads etc. 26" varmint contour. Very frustrating. I'll stick with my trusted Kreigers from now on.

 

[eklarsen]

what was the temp when you were getting higher velocity compared to when you are getting lower speed?

 

[Greyfox]

Not sure if it's the same issue but I have a 6.5x284 that I had worked up a an accurate load at 3000FPS. At 250 rounds the accuracy fell apart and I have not been able to restore it. Velocity was slightly lower. Tried every thing. Copper removal, different loads etc. 26" varmint contour. Very frustrating. I'll stick with my trusted Kreigers from now on.

My throat remains unchanged with the seating depth to ogive unchanged. Crown is perfect. Tested temperature range +/- 10F. Well proven load, nothing radically different. I haven't checked it with a bore scope.
Wrote the barrel of as NG.