Ladder Test Confusion, 6.5 PRC

[Randy Tidwell]

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

 

[david g ranes]

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

Sure you didn't get your numbers on shells mixed up. David you

 

[MagnumManiac]

First cold bore shot can be higher.

Cheers.

 

[Randy Tidwell]

Sure you didn't get your numbers on shells mixed up. David you

Nope, positive I kept them on order.

Understand cold bore difference, i fired two fouling shots prior turning the chrono on. I just never seen that much increase.

Will see what happens Sunday.

 

[L.Sherm]

Your numbers are tell me 58.0 your max'd out or your gun doesn't like that powder unless target says different.

 

[Varmint Hunter]

In my limited experience, if you do the exact same ladder test more then once you can get different results. I've experienced this more then once.

Maybe a second ladder will be more revealing.

 

[coop2564]

Is barrel broke in completely? Could be it was copper fouling up slowing it down if its still rough.

 

[Dmagna]

You are over your max charge weight

 

[Quintus]

I am running the 121HH from an 8 twist 24" with RL 26. I had similar readings from 58.3 to 58.9 grains. I had a taller ladder to shoot running my ladder up to 61.6 grains and from 59.2 up to 61.6 I got more predictable, anticipated results. I never did have any pressure signs with no stiff bolt lift and primers looked the same at 57.0 grains as they did at 61.6. At 58.3 grains I was at 3303 and topped out at 3493 at 61.6 grains. I shot groups at 59.5 grains and 3375FPS and 200 yard 5 shot groups averaged 1.5". Then shot groups at 60.8 grains at 3460fps and groups shrunk to just a smidge under or right at 1". I probably can't shoot better than that so I am tickled. Have you run a ladder past 59 grains?

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

 

[Mikecr]

Was the brass fire formed to stable capacity?

 

[redchinviking]

Tagged in here. I had similar results a few weeks ago with the 124 HH in 6.5 prc but with h1000 and in .5 gn increases. Velocities went down for quite awhile before coming back up. Labradar. Flat spot on paper was the same as with the velocity and the node proved a super consistent 1/2 moa all the way out to 600 so far.

 

[L.Sherm]

How many rounds are on your barrel?

 

[Randy Tidwell]

You are over your max charge weight

I'm getting no pressure signs, primers are not flat, mic'd the cases, grew approx .0002 to .0003.

I will agree, the barrel is new, approx 45-50 rounds so far.

No signs of copper fouling, I am pretty anal about cleaning. Barrel was broke in by cleaning after each round for 5 shots, then after 2 shots for the next 10.

Was the brass fire formed to stable capacity?

Yes

 

[Randy Tidwell]

Tagged in here. I had similar results a few weeks ago with the 124 HH in 6.5 prc but with h1000 and in .5 gn increases. Velocities went down for quite awhile before coming back up. Labradar. Flat spot on paper was the same as with the velocity and the node proved a super consistent 1/2 moa all the way out to 600 so far.

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.