Advice interpreting a ladder test result

[charliehorse27]

Good morning everyone,

I watch and read quite a bit of the forums on here and perhaps you all can give me an idea of what I'm looking at.

I have a Seekins Precision Havak PH1 in 300 WM that I've had trouble finding a suitable load for. Using the Berger 215 Hybrids, load length tests showed it liked .005 off the lands. Then I proceeded to try a ladder test with H1000.

These results were conducted at 380 yards at a bench with a front bipod and a sandbag rear rest.

I started at 74 gr and went up in .4 gr increments. I got sticky bolt lift at 80.2 gr and it started getting wild so I quit there. I do not have any velocity data for them; I have a Magnetospeed and it seems to affect the barrel harmonics when attached so it was not used at this point. All of these were using the same point of aim.

From what I can tell, it looks like 75.2 - 76 may be a useable node (depending on velocity) but I'm hoping 77.2 - 78.4 will also be accurate, and fast.

What I'm not sure about is why so many of these were on the same vertical plane (or nearly) despite the distance.

 

[rsmithsr]

how much l/r wind did you have ?
you have discovered the error of a magneto speed.
try mounting next to the muzzle on a rod and base.
nice target, 75./76 looks good reshoot
77/78 is not as food but i would reshoot
reshoot= 3 shot group from the middle of the load
(or 3x3 across the load .4 step)
then play with jump or jam, unless a hunting rifle

 

[Buckreed]

Odd that a 74.4 is above a 79.2. If you have access I would shoot this again at a longer range to make the vertical spread more defined. It could also be in consistent cheek weld messing with your vertical.

 

[Dmagna]

You have the speeds?

 

[26Reload]

Looks like 74.4-74.8...
And yes...cheek weld....it welds us all once in a while.....i am getting used to a new iota stock with a rising comb.....takes a little adjusting.....

 

[L.Sherm]

I also like 75-76, I think you will find a good one around 75.5

 

[TRG65]

I'd definitely play with the 75-76 range. If you have a good chronograph, I'd run 2 or 3 at each .1 from 75 to 76 and see where it works out the best. If you download 6.5 guys spreadsheet it does all the math and graphing for you.

 

[rsmithsr]

would not

I'd definitely play with the 75-76 range. If you have a good chronograph, I'd run 2 or 3 at each .1 from 75 to 76 and see where it works out the best. If you download 6.5 guys spreadsheet it does all the math and graphing for you.

 

[charliehorse27]

There wasn't any wind at the time when I was shooting. I also thought it odd the 79.2 was the same vertical height as the rest. It was wide right and I was confident I didn't yank it. I wondered if it could have been due to max pressure?

How would inconsistent cheek weld cause the unexpected verticals? Just not getting the same sight picture every time? The stock comb height is low due to the 20 MOA scope rail, so I have an adjustable stock pack on there to raise it.

I'm curious what the speeds will be between 75-76.

 

[dok7mm]

The fact that you have so much horizontal in your ladder, under good conditions, leads me to believe your vertical is suspect also. More than likely, shooting off the bipod, with a 300 wm, could cause some vertical distortion.

I'd try it with a good front/ rear bag set-up. It takes awhile, but I always let the barrel cool to ambient temperature between shots.

Not being able to check velocities of your ladder is a bummer, this is exactly why I went to a LabRadar years ago.

Hope your next ladder gives you a good result.

 

[25WSM]

For 380 yards I think the verticle looks pretty good. I'm not sure why it's so wide. Usually wind but you state it was calm. Do a 75 to 76. 3 each at 2 tenths apart. Find best part of that node. I'm betting 75.6 or 75.8 and then do another seating test. Ladder to find node and seating to tighten groups. Once I find my seating depth I usually go up a 10th and down a 10th to see if it's better or not. Don't be afraid to jump that bullet. They are not picky.
Shep

 

[SinCityJets]

Hey everyone! FNG here. 1st post. Don't listen to anything I say, I'm a complete nobody.

To the OP, you said your gun liked the bullet set to .005 off the lands. How far out did the up test it. Did you go out to .090? Or at least .040?

Check out the latest 5 articles on Precision Rifle Blog. I think the reasoning behind your shot placements are in this research. I know the developer of the Ballistic-X App is currently making some changes to his app that will extrapolate the data to make it easier to see what your fun is telling you with these different "ladder" tests.

What the current research is showing, is that the first test should be running your jump from .005 out to .090. Once that node is found, then go to powder charge.

Please re-read my first paragraph!

Good luck!

Chad

 

[rsmithsr]

I would not spend time and money on a new ladder. test what you have, you have clear spots to load and check the results.
small vertical at this distance is a good thing.

 

[corsair4360]

I have tried the ladder test mulitple times, never found the results useful out to 300 yards at our local range (as far as it goes). I suspect shooter error (mine) is part of it. I have gone back to 5 shots for my 6xc's and 3 shots for my hunting rifles (a 270 WSM and a 338 Win Mag).