New Lapua 6.5 CM case firings

[6.5 forever]

My first two firings with this box of Lapua are running 10 fps slower than 2 other boxes of the same lot number with 10 firings.
What is your experience with the number of firings to get brass up to speed?

 

[L.Sherm]

How does it shoot?

 

[6.5 forever]

Not nearly as well

This is a new barrel. I have shot 3 five shot groups out of it with the old brass. This is the largest. Speed with the old brass is 2840 and only 2827 with the new. 2827 groups are .5.

 

[1K6BRA]

You should be grinnin like a possum eating yellow jackets if that is 100 yards. If it is further out than 100 yards eat more yellow jackets and keep grinnin!

 

[6.5 forever]

This is a special barrel. It is about 25 fps faster than any barrel I've had. 2840 is the fastest I've ever had. And it shoots.....no pressure at all. H41.4 H4350, 142 SMK, CCI 450.

But 2827 opens right up... Two more groups I shot Saturday (yes 100 yards). I only shoot 100 yards for POI verification. Other shooting is steel out to 1000.

 

[Hengehold]

I think 10 fps and your sample sizes are so small that you are within the noise of statistical variation.

Add that to the fact that it is being tested in your new barrel and that can account for any real variation that may be found

In other words, after barrel has been broken in (100-200 rds fired), and a statistically valid sample size for avg MV (40+ rds) you can review the data to look for anomalies.

 

[JMayo]

.02 more powder will get 20fps, will it not?

 

[L.Sherm]

Add a .1gr and see what it does, like noted it may speed up at 100-200 rounds very well could be why it is a little slower.

 

[RegionRat]

To get a rough idea of the powder step it takes to see a 10 fps change.

Here is the typical Hodgdon web site data

If we take the simple approach to scale the equivalent powder change to see roughly what it takes to get a 10 fps difference.
(2694 - 2573)/(41.5 - 38.8) = 44.8 fps per grain, so then 10/44.8 = roughly 0.22 grains

I wondered about the same questions as @Hengehold
A 10 fps difference isn't much in some ways, and how meaningful it is depends on his point.

If your load tune window is only 10 fps wide and then makes you unhappy, you end up with a real challenge to hold it.

It isn't impossible, but it is difficult to pre load ammo in different sessions, store it, transport it, etc., and still keep the speed exactly. We even have temperature, weather changes, barrel condition, etc., to manage.

If the averages of the first brass were really solid and had a good sample size behind them with a small SD, then we have a decent baseline.

I'm not discounting a 10 fps difference, just that it takes some real solid baseline with a very tight SD to say the different brass batch was really to blame.

Is the 10 fps difference more than an one SD away between the two averages?

Without taking an in depth look at your actual speed data for both batches of brass, you can get a preview of the statistical significance based on the SD. If your 10 fps difference isn't more than 1 SD away on the averages, the two batches are likely in family and the issues are from under-sampling.

If you have solid stats behind your baseline with a tight SD of less than 10 fps, and you have more than 15 samples of speeds from 2X fired brass on the next batch that is different by more than 1 SD, you can run a statistical test to see if those two are really different. (Or we can run that test for you)

Is the powder still producing the exact average speeds between the two brass batches?
If it is, then it would be time to examine the internal capacity of the brass, anneal both, check the condition inside the necks, check the thickness, and then re-test.

We can even get a difference in speed if we allow the powder's water content to change, but we would find that issue by loading them both at the same session and see if the difference still exists.

At the same time, I agree with @1K6BRA , nothing wrong with the groups in those photos.
Kudos for keeping the pencil sharp and working on good shooting.
Merry Christmas and Happy New Year!!!

 

[L.Sherm]

There only one way to find out add.1 and shoot it everything else being equal.

 

[6.5 forever]

To get a rough idea of the powder step it takes to see a 10 fps change.

Here is the typical Hodgdon web site data
View attachment 1616300
If we take the simple approach to scale the equivalent powder change to see roughly what it takes to get a 10 fps difference.
(2694 - 2573)/(41.5 - 38.8) = 44.8 fps per grain, so then 10/44.8 = roughly 0.22 grains

I wondered about the same questions as @Hengehold
A 10 fps difference isn't much in some ways, and how meaningful it is depends on his point.

If your load tune window is only 10 fps wide and then makes you unhappy, you end up with a real challenge to hold it.

It isn't impossible, but it is difficult to pre load ammo in different sessions, store it, transport it, etc., and still keep the speed exactly. We even have temperature, weather changes, barrel condition, etc., to manage.

If the averages of the first brass were really solid and had a good sample size behind them with a small SD, then we have a decent baseline.

I'm not discounting a 10 fps difference, just that it takes some real solid baseline with a very tight SD to say the different brass batch was really to blame.

Is the 10 fps difference more than an one SD away between the two averages?

Without taking an in depth look at your actual speed data for both batches of brass, you can get a preview of the statistical significance based on the SD. If your 10 fps difference isn't more than 1 SD away on the averages, the two batches are likely in family and the issues are from under-sampling.

If you have solid stats behind your baseline with a tight SD of less than 10 fps, and you have more than 15 samples of speeds from 2X fired brass on the next batch that is different by more than 1 SD, you can run a statistical test to see if those two are really different. (Or we can run that test for you)

Is the powder still producing the exact average speeds between the two brass batches?
If it is, then it would be time to examine the internal capacity of the brass, anneal both, check the condition inside the necks, check the thickness, and then re-test.

We can even get a difference in speed if we allow the powder's water content to change, but we would find that issue by loading them both at the same session and see if the difference still exists.

At the same time, I agree with @1K6BRA , nothing wrong with the groups in those photos.
Kudos for keeping the pencil sharp and working on good shooting.
Merry Christmas and Happy New Year!!!

Thanks for the indepth explanation. My cases are annealed every firing and the only difference is the number of firings, same lot number. The groups in the picture are fantastic . The groups with the three times fired cases are not. If the new cases need more firings I will shoot them in my back up.

 

[C.E.Smith043]

Thanks for the indepth explanation. My cases are annealed every firing and the only difference is the number of firings, same lot number. The groups in the picture are fantastic . The groups with the three times fired cases are not. If the new cases need more firings I will shoot them in my back up.

What are your thoughts about not annealing them for a few firings and see if the fps goes up

 

[L.Sherm]

On Lapua and ADG I dont anneal at all.