Ladder Test Confusion, 6.5 PRC

[7mmTikkaShooter]

I'm confused?

Did a 10 shot ladder test for my Ruger No. 1 6.5 PRC.

Load Data:
6.5 PRC, 7.5 Twist, 27"
124 Hammer Hunter
Federal 210, ADG Brass turned to .014" thick (rifle has a .295 neck).
RE26 starting at 58 grs, increased .1 grs to 58.9

Brass has been prepped in detail, trimmed to .001" length.

I've done many ladder tests, bur this one has me confused.

Labradar results:
58.0 = 3343 FPS
58.1 = 3337 FPS
58.2 = 3301 FPS
58.3 = 3309 FPS
58.4 = 3300 FPS
58.5 = 3289 FPS
58.6 = 3304 FPS
58.7 = 3232 FPS
58.8 = 3397 FPS
58.9 = 3304 FPS

My confusion is why did I get 30+ fps faster with .2 less powder. Haven't see that before?
Load 7 was 70 fps slower, I'm attributing that to a bad read by the chrono.

Throwing out load 1, 2, & 8, I get ES of 19, SD of 6.2

58.3 grs seems to be the flat spot and I am happy with velocity, will start playing with seating depth with that load.

Graph attached.

What are your thoughts?

Randy

I think you'd be best to replicate the test at least once more. You really need at least 3 replications for scientific data anyway, and when you're looking at a ladder test it's best to have enough good data that you can rely on it and not try to see pictures in the clouds. Pretty sure someone else has stated it but is this virgin brass or are there any differences in number of firings? Might look at water sorting some brass to be sure that isn't another variable. In general most of these velocities seem pretty flat so it looks like you're in a good charge range.

 

[LongBomber]

Mixed brass or bad chrony readings?

 

[Randy Tidwell]

All the same ADG brass. Prepped carefully.

 

[L.Sherm]

I've seen this twice, first time was a 338WM and RL19 no matter how much powder I put in the case would go any faster than 2800 with 210NP.
Secound time with the barrel that is currently on my 30-28 no matter what powder and how much 3000fps with a 215 i was just about to jerk the barrel off and start over took it out on last time and it just woke up so to speak. Probably at that point was 100-125 rounds, never coppered or anything just a dog then boom, go figure.

 

[Randy Tidwell]

I've seen this twice, first time was a 338WM and RL19 no matter how much powder I put in the case would go any faster than 2800 with 210NP.
Secound time with the barrel that is currently on my 30-28 no matter what powder and how much 3000fps with a 215 i was just about to jersey the barrel off and start over took it out on last time and it just woke up so to speak. Probably at that point was 100-125 rounds, never coppered or anything just a dog then boom, go figure.

That what I'm thinking. Stop trying to work up a serious load till I get 100+ rounds down the tube.

Just impatient lol.

 

[L.Sherm]

That what I'm thinking. Stop trying to work up a serious load till I get 100+ rounds down the tube.

Just impatient lol.

I know it can be frustrating

 

[redchinviking]

I was just over a hundred rounds on my CA barrel when I started the load development for the Hammers FYI . And my brass was once fired hornady neck sized only with .003 neck tension. It's been shooting great though so no complaints but I was definitely scratching my head at the time. I'm a "screw it, let's go take it hunting now" kind of reloader but I was definitely wondering what the explanation might have been.

 

[jfolanddvm]

The test is confusing but so is the math. If your numbers are correct, your extreme spread, taking out shots 1,2&8, would be 108 (shot 9 {3397} minus shot 6 {3289}). SD would be just under 15.6. But if you throw out the outliers (shots 8 and 9) there really isn't much change from 58.2 to 58.9 gr. Node or max charge?

 

[Randy Tidwell]

The test is confusing but so is the math. If your numbers are correct, your extreme spread, taking out shots 1,2&8, would be 108 (shot 9 {3397} minus shot 6 {3289}). SD would be just under 15.6. But if you throw out the outliers (shots 8 and 9) there really isn't much change from 58.2 to 58.9 gr. Node or max charge?

The math came off the Labradar.

I've run out of time for another ladder test, I settled on 57.0grs of RE26.

Avg 3264fps, SD 16.5.

3250, 3259, 3282 fps
ES 32, SD 16.5

Shot pretty good, just under 1/2" (two touching, one just high) nothing to shout about. But I'm going to run with it.

I will follow up on this post after the Elk hunt when I do another ladder test.

PS, bad hair day, LOL.

 

[jfolanddvm]

The math came off the Labradar.

I've run out of time for another ladder test, I settled on 57.0grs of RE26.

Avg 3264fps, SD 16.5.

3250, 3259, 3282 fps
ES 32, SD 16.5

Shot pretty good, just under 1/2" (two touching, one just high) nothing to shout about. But I'm going to run with it.

I will follow up on this post after the Elk hunt when I do another ladder test.

PS, bad hair day, LOL.

Good luck on your hunt!

 

[Hard rock]

I havnt tried H1000 yet, only have 1 1/2 pounds left, keeping that for my RUMS.

Leaving for an Idaho Elk hunt on the 8th. Area we will hunt is Farley short range, long shot is about 300yds. 58 gives me approx 3300fps.

I will be very happy at about 3250fps.

Will report back tomorrow.

I am hoping to get the PRC sorted out tomorrow. Just see how it shoots with lighter loads I backed off to 57.0, 56.3, 56.6 for tomorrow's test. So far I've shot all the way up to 59.8 w/RE26.

58.3 hrs of n165 with a cci250 mag primer is my 124 gr hammer load 6.5 prc 26 in 1-8 twist it's n165 is faster than r26 I have no pressure problems 3300plus fps 3452 with 63.5 hrs n165 and the 123 gr absolute hammer your load doesn't sound like it should be over pressure I would start my ladder test over

 

[Hard rock]

58.3 hrs of n165 with a cci250 mag primer is my 124 gr hammer load 6.5 prc 26 in 1-8 twist it's n165 is faster than r26 I have no pressure problems 3300plus fps 3452 with 63.5 hrs n165 and the 123 gr absolute hammer your load doesn't sound like it should be over pressure I would start my ladder test over

Good luck on your hunt sounds like a good enough load

 

[Randy Tidwell]

The test is confusing but so is the math. If your numbers are correct, your extreme spread, taking out shots 1,2&8, would be 108 (shot 9 {3397} minus shot 6 {3289}). SD would be just under 15.6. But if you throw out the outliers (shots 8 and 9) there really isn't much change from 58.2 to 58.9 gr. Node or max charge?

JF,

I am also confused on the math. I am only doing this as a exercise in math.

Using Excl's Standard Dev formula (=STDEV.s(A1:A7), I get 6.1 SD, 19 ES, this matches the Labradar pretty close.
I kept shot 9 in the mix, as it was only 3fps slower than the 3300fps average.


3301
3308
3300
3289
3304
3297
3304

58.3 hrs of n165 with a cci250 mag primer is my 124 gr hammer load 6.5 prc 26 in 1-8 twist it's n165 is faster than r26 I have no pressure problems 3300plus fps 3452 with 63.5 hrs n165 and the 123 gr absolute hammer your load doesn't sound like it should be over pressure I would start my ladder test over

Been looking for some N165. Like everything else, short supply.

 

[jfolanddvm]

Using Excl's Standard Dev formula (=STDEV.s(A1:A7), I get 6.1 SD, 19 ES, this matches the Labradar pretty close.
I kept shot 9 in the mix, as it was only 3fps slower than the 3300fps average.


3301
3308
3300
3289
3304
3297
3304

That explains my confusion - shot 9 in original post was 3397, not 3297 - now it makes sense (at least the math does