Ladder test question

[Gatr]

338 lapua, lapua brass, 300 berger, rl33, cci 250
Loaded up a ladder test at .3 gr increments. Shots 1,3,5,7 all went in the same hole.
Shots 2 and 4 went in one hole 3/4" away. There seems to be a node there, but the every other shot thing has me scratching my head.I'm a not sure what to do next. Maybe a ladder test at .1 increments?
Any advice?
Thanks

 

[FearNoWind]

Not sure how you conducted the test and what 3/4" "away" means. Ladder testing data relies on vertical dispersion so if "away" means wide of the other shots it's a non issue.
lightbulb Try this:
Establish a series of horizontal lines about six inches apart and divide them with a single vertical line. Use the lines to center your point of aim for a five shot series, each with a different load. Measure the center of the distance of each round from the horizontal line used t to aim the shots for each group. Average those and work with fine tuning the CBOL of the group with the lowest average.

 

[Gatr]

Thanks for the response.
Shots 1,3,5,7 went in the same hole.
Shots 2 and 4 went in one hole 3/4" above. The rest of the shots had significant vertical spread, making a 2" group.
I'm not sure what charge to load five shot groups at.
Normally during a ladder test I find 2 or more consecutive shots that have no vertical dispersion and use those charge weights to load test groups.

 

[8andbait]

at what distance did you shoot your ladder?

 

[Mikecr]

Gatr, had you tested for best seating before running the ladder?
I do not agree with FearNoWind -that's not a ladder test.
And there is no reason to discount horizontal. It should be considered just like vertical. A muzzle is not just whipping. It's bore expanding/contracting, whipping, twisting, releasing pressure against bullet bases, and recoiling in any number of ways.

A ladder doesn't just help with load decisions. It's also a diagnostic test for your shooting system(including scope, mounts, rest, bedding, cartridge/gun design, reloading of every sort, shooting ability, understanding, etc).
When a ladder doesn't make sense, its because you're not ready for it.

 

[Engineering101]

Gatr

0.3 grain increments in a 338 Lapua is almost like no change. I'd do 1 grain increments. I agree you have found a classic antinode. You should see the group sizes change over a 5 grain or so range. Just last week I helped a friend do this. His shots started over 1 MOA and gradually tightened up to 0.5 MOA as he hit the top of the ladder. He was lucky that max velocity corresponded to max accuracy but sometimes it works that way too.

 

[Gatr]

Thanks for the responses.
This was at 100 yards.
I loaded up a mini ladder at .1 gr increments and shot it yesterday. I had much better results. 3 shots in the same hole with an Es of 12. I think I found a node.

 

[ColoYooper]

Gatr, at 100 yards, how much variation in shot placement do you expect to see between two shots that differ by 20 fps? With the photos you posted there is NO WAY that difference is outside your 100 yard group size. Performing the ladder test at 100 yards does nothing but wear out your barrel and waste money. The Ladder test needs to be performed at a distance where the variations in velocity can be observed, as well as variations in barrel ring harmonics. YOU WILL OBSERVE NEITHER AT 100 YARDS!!! (yes I'm shouting). Perform the ladder test at 600 yards and the variations in shot placement due to velocity will begin to cluster with variations in barrel harmonics. Then select the center charge for that cluster and you will be happy. I've done dozens of ladder tests and here is the best result I could ever hope for: (see attached) NOTE: There are bands where a faster bullet has left the barrel while the harmonic ring is at the bottom of its period, which groups with a slower bullet that has left the barrel while the harmonic ring is at the top of its period. NOTE2: The picture is rotated to 90 degrees to the left! NOTE3, there were variable winds of 6-12mph from 9:00 on that day, and I chose to just hold the 6 mph MIL setting. NOTE4, In case you've missed it, the Ladder test does NOT concern itself with horizontal dispersion. The purpose of the Ladder Test is to find a "SWEET" charge which will automagically correct itself for a hot charge, by exiting the barrel at the bottom of it's harmonic period, and a light charge, which will exit the barrel at the top of it's harmonic period, and hopefully group in the same VERTICAL position. NOTE5, this is a VERY CUSTOM 300 WM shooting Berger 230 gr Hybrids. I have only seen results this conclusive once...even with this rifle. So don't be discouraged if your results don't match. Most of the time it's like reading tea leaves...but give yourself a chance, and read those tea leaves at 600 yards.

 

[ColoYooper]

NOTE6: Attempt to identify and circle horizontal bands of adjacent shots. These bands should be separated by over an inch. Again, most of the time I've needed to discount a flyer or 2 or 3. Then select the average charge of the largest band. In my case it was the second band which had 4 shots. I took the average charge of the 4 shot (of which none of the actual 4 shots where)