Odd ladder test results. Next step advise wanted.

[Quietcro]

This is my first set of handloads and my first ladder test. This is a hunting only load. All screws torqued before firing and verified tight after. Point of aim is center dot. 300yd target. Prone with TBAC bipod and rear bag. Lateral correction between shots 1&2.

My question: the rounds stopped displaying a standard ladder test result and started to jump vertically after round #5. It can be seen in the target picture. Is this normal for a lite barrel? I feel like there is something I’m missing.

Rifle:
Tikka T3 WTO switchlug
T3 lite stainless barrel
McMillan Gamehunter Ultralight
Leupold VX5

Handload:
300 WSM
180gr Swift A-frame
Virgin Nosler brass
RL-23(not 26 like the target says)
Remington magnum primers
Seated to 2.727 CBTO (0.050 jump)

Magnetospeed V3 (not barrel mounted)
RCBS matchmaster dies
Chargemaster 1500
All brass was put through sizing die and in/out camferred before loading. All CBTO within .001.

#- grains RL23- velocity

1-61.5 - 2797
2-62.0 - 2833
3-62.5 - 2855
4-63.0 - 2890
5-63.5- 2897
6-64.0- 2916
7-64.5- 2940 snug bolt
8-65.0- 2972
9-65.5- 2980
10-66.0- not fired

No serious pressure signs through the test. My plan ahead is to do a seating depth test at 63.5. 3-round groupings moving in at .005 each and shooting round-robbin. I have plenty of COAL before maglength is an issue. Any other advise? Thanks for any input.

 

[BBVDD]

63.5? Looks to me like 62 - 63 is a node

Well, now that I look at your written notes the speeds are different than what you typed out.

 

[Quietcro]

63.5? Looks to me like 62 - 63 is a node

Well, now that I look at your written notes the speeds are different than what you typed out.

Edited.

 

[canezach]

Just based on velocities, albeit a very small sample size and with virgin brass, I'd split the difference between 63.0 and 63.5 grains. Your velocity only rises by 7 fps over 0.5 grains. I would load up a few rounds of each charge weight from 60.0, 60.3, and 60.6 to see if it's repeatable. If so, I'd venture to say all the velocities from those charge weights will fall within 20 fps of each other. Of course, then you'll have to re-chrono your loads with once- fired brass and adjust from there.

 

[Rocketmandb]

Just based on velocities, albeit a very small sample size and with virgin brass, I'd split the difference between 63.0 and 63.5 grains. Your velocity only rises by 7 fps over 0.5 grains. I would load up a few rounds of each charge weight from 60.0, 60.3, and 60.6 to see if it's repeatable. If so, I'd venture to say all the velocities from those charge weights will fall within 20 fps of each other. Of course, then you'll have to re-chrono your loads with once- fired brass and adjust from there.

This.

 

[Quietcro]

Problem found. The neck bushing I received is the wrong size. Those rounds had basically no neck tension.

I just pulled apart the second ladder I built. Trust but verify. Measure twice, cut once.

Thanks for all the input.