0.308 EC Tuner Brake confirmation with IMR 4064 & Scenar-L 175gr bullets

[AntiMedic]

I shot this yesterday finishing fire forming some virgin brass.
Rifle information:
Gun – Prison Sex, Big Horn TL3-SA, Bartlein 22” 5R SS 1/10 EC tuner brake, 0.308, KRG X-Ray GEN III, NF ATACR 5-25X56 F1 T3 Sphur 4001 mount
Load – Alpha Munitions brass, IMR 4064 @ 40.7gr, BTO 2.1510, CCI 200, Lapua scenar-L 175gr
Weather – T: 83.0 P: 28.27 H: 45.9 DA: 3695
Target was at 284 W
Sun to the south and wind coming in from around 290

First was zeroing the rifle as I switched the chassis and scope.


Next is the gross tuner shots IE 0, 2, 4, 6 etc


Next is the fine tuner shots at 2, 2.5, 3 and 3.5 for confirmation


I called the flyers. Next is out to 300yds which a totally messed up and left the tuner on the last setting. I should have set it to 2.5. Whoops my bad.

This showed a group size of 0.664

This showed a group size of 0.782

I am not confident in the accuracy of my powder drops. It is virgin brass but the spread in MV is a bit much. For the brass prep, I ran a 0.306 mandrel through the cases. They are already annealed. The bullets are sorted by base of bullet to ogive and seated to 2.1510. For this box I dropped to 40.6 and then trickled up to 40.7. I am trying to narrow down what is causing the ES of the MV. Any help, suggestions etc are appreciated.
Here are the stats from all rounds fired yesterday:

2579​	2593​	2580​	2615​	2579​	2565​
2607​	2602​	2536​	2584​	2608​	2580​
2631​	2579​	2543​	2613​	2583​
2586​	2579​	2609​	2618​	2608​
2582​	2605​	2585​	2601​	2611​
2591​	2591​	2585​	2621​	2629​
2581​	2602​	2571​	2585​	2620​
2588​	2609​	2597​	2606​	2618​
2615​	2579​	2549​	2603​	2575​
2596​	2614​	2578​	2611​	2556​
Average	2592.904​
MAX	2631​
MIN	2536​
ES	95​
SD	21.09294​

 

[boltfluter]

Personally, I would not pay attention to anything until all the brass is fire formed. Rerun the test, fix your mistakes, and I would bet your numbers will be better. Good luck!

Paul

 

[AntiMedic]

@boltfluter Thank you for the advice. That is what I am crossing me fingers for. I also read this thread here https://forum.accurateshooter.com/t...muzzle-velocity-spreads.4045435/post-38157266 and have been systematically attacking issues.

 

[SweaterDood]

As previously stated, repeat on fireformed brass. Also you might want to chrono a small ladder test. Your 40.7gr may not be in a good node for that particular combination in that rifle. Most decent electronic scales resolving within 0.1gr are more than good enough. The wiggle room a good node provides you is enough room to “throw ‘em” and maintain good ES.

 

[AntiMedic]

I did chrono a small ladder test with good results. I swapped out my trigger assembly as it’s overdue and more than likely worn out. I am headed out tomorrow to test it.

 

[Bill Norris]

Personally, I would not pay attention to anything until all the brass is fire formed. Rerun the test, fix your mistakes, and I would bet your numbers will be better. Good luck!

Paul

Great advice Paul.