Sudden change in SD/ES?

[Hollywood 6mm]

I recently switched lots of Varget for my 223 trainer reloads (80gr ELD-M over Varget with WCC brass and FGMM SR primers), and did a quick velocity check. The first 3 rounds looked great, and only a few FPS slower than the old lot - then the wheels fell off. I ended up running 10 rounds over my Magnetospeed V3 and had an SD of nearly 30 and an ES approaching 70 from the same load that previously gave single digit SDs and ES around 20. I had some leftover ammo loaded with the old lot of powder with me, and ran them over the chrono, as well - with the same results. 2-3 shots would be in the same velocity range as before, then one shot 30-40FPS slower, and one as much as 80FPS slower, then a couple back at normal speed. The same chrono gave me a 5SD with my 6 Creedmoor reloads just a few minutes before the 223 test, and there's no signs of a bullet strike on the bayonet.

Other than my 223 barrel suddenly letting go at ~4000 rounds, is there something I could be missing? Groups on paper looked typical for this rifle and ammo (roughly .5MOA), and the barrel was cleaned about 100 rounds ago after a couple thousand rounds of consistent performance without cleaning.

 

[lash]

Just for kicks, test a few more rounds of the 6 Creedmoor just to verify that the MS is reading correctly.

 

[Hollywood 6mm]

Just for kicks, test a few more rounds of the 6 Creedmoor just to verify that the MS is reading correctly.

I won't be able to check it for a few days, but the velocity I got from the MS was in line with previous checks, and data down range matched up perfectly with the MS and Kestrel. Right now, I suspect it's barrel related, not Magnetospeed. After the match this weekend, Ic an try a new run of load development and see if I can get the SD and ES back under control. I'm just hoping it's not a dead barrel after only 4k-ish rounds.

 

[lash]

Well, for your sake I hope that it’s not the barrel, but I wouldn’t hold your breath.

On the plus side, maybe your load just wandered out of its accuracy node a bit and needs tweaking.

 

[Hollywood 6mm]

Well, for your sake I hope that it’s not the barrel, but I wouldn’t hold your breath.

On the plus side, maybe your load just wandered out of its accuracy node a bit and needs tweaking.

I'm hoping for the latter but expecting the former. Even if it's the barrel, I can't complain too much since it's more than paid for itself in training time vs burning up 6CM barrels, but I was hoping it would last a good bit longer.

 

[_Raining]

I had some leftover ammo loaded with the old lot of powder with me, and ran them over the chrono, as well - with the same results. 2-3 shots would be in the same velocity range as before, then one shot 30-40FPS slower, and one as much as 80FPS slower, then a couple back at normal speed.

Sounds like you verified that it is unrelated to the new lot of varget.

 

[Hollywood 6mm]

Sounds like you verified that it is unrelated to the new lot of varget.

Definitely not the new lot. I'm hoping that throat erosion somehow caused a shift in the node, but I'm not usually that lucky.

 

[Dag34]

Double check the magneto speed and put some new batteries in it too.

Good luck, I hate chasing stuff like this.

 

[Sheldon N]

I say it's a trainer, beat that red headed rifle into submission until it stops hitting targets then order a new barrel.

A while back had a training day with a buddy who's a top level national shooter. His trainer was not running right, carboned up suppressor or barrel or something, losing velocity don't remember what. I just remember that about half way through the day his gun started shooting 0.3 low. He was a bit confused by it, then just added 0.3 to his dope and kept kicking our butts. Then a couple hours later same thing again, he spins the turrets a few clicks and goes back to crushing it.

I just finished up a lot of XBR8208 in my 223 trainer this week, and last night went to load more ammo. I stared at the new 8lb jug of a different lot number and thought to myself.... I really should run an OCW to see how this shoots. Then I decided.... ah screw it and loaded up 300 rounds on the Dillon.