Anyone use a ladder test for load development?

[fatbacks]

So I am mostly doing this out of curiosity and as a learning experience. I wanted to see if I could use a ladder test to hone in on a good load. I am using leftover components that I don't want to use for my hunting load. Secondary goal was to see if I could get a lot of velocity out of Superformance as advertised ( Spoiler, I didn't - not sure if it was because it was super cold out).

A little about the rifle: Tikka T3, 300 WSM, 22" Barrel. Probably has a few hundred rounds through it over the past 12 years.

Weather: About 10 degrees, snowing lightly with freezing fog.

Loaded 11 rounds in .5 gr increments up until nearly the max load published in the Hornady manual. No pressure signs even at the top end today. Used magnetospeed for my chrono.

Results:


So questions on where to go here and what I was thinking about doing:

• Should I go back to the range and keep going if I didn't find any pressure signs at 74 gr of charge weight to see if I can find a higher velocity node?
• Am I correct in thinking there are velocity nodes from 70.5 gr to 72 gr and 73 gr to 74 gr?
• Should I load up some rounds with 73.5 gr of powder and see if they group?
• Does anyone have any real world experience with Superformance and temp stability? Am I going to gain a bunch of velocity this summer when its warm out?

Anyhow, I guess I am looking for some tips from guys that use this method.

My desired combo for hunting with this rifle is 150 gr Accubonds over H4350 in Nosler brass. I have all those components on hand but didn't want to use them up trying them out on a ladder test if it didn't prove useful to me.

 

[Cahunter805]

From your velocity it looks like around 71gr and 73.5gr are the nodes but you need to retest.
Where is the target? What distance was this shot at? How far from the lands? Was the magnetospeed mounted on the barrel?

 

[tdhanses]

Personally I like your 71.5 - 72.5 velocity. What you want is to find an area where velocity doesn’t swing much. I would go with 72gr and then load at a min 3rd of each only changing seating depth in each 3 shot group or even 5.

Also if you had zero pressure signs at 74 I would test 74, 74.25, 74.5, 74.75, 75, 75.25 and 75.5. If you see signs immediately you know to test no further.

After you do your seating depth you could then do another ladder test at 71.5, 71.75, 72, 72.25 and 72.5. Again looking for the lowest velocity swing between.

I like to shoot so unlike some I’ll dump 100rds to fine tune a load.

When I do a ladder test I don’t even setup the chrono, I shoot 10rds at 200 yards (100 yards is not far enough to see shot variance) to the same point keeping track of where each shot impacts. I don’t care about the distance between shots left and right, I’m only watching for a string or strings that are hitting in the same or smallest distance up and down, look for the loads on the same plain within a similar load.

I’ll then fine tune the next ladder between these spots or just pick a load in the middle and start doing the seating depth tests. I’ll then start to chrono final loads to make sure my SD and ES is low.

Now you can’t do this from the single ladder tested loads just for velocity, you can’t really measure SD or ES till you load up a bunch of the same exact loads and chrono them.

 

[fatbacks]

So here is the target. I was under the assumption that grouping on this was not critical... also magnetospeed on a sporter barrel tends to throw them off. The bullets started high left and worked their way downwards and right. I was going to find that velocity node and then load up enough rounds to see if it groups around that node and then play with seating depth after that.... think that'll work?

 

[Axlrod]

I have used this method on a lot of rifles and it works
https://www.longrangehunting.com/threads/tuning-for-long-range.192998/

 

[Cahunter805]

I tend to do my tests somewhat like TD. I would recommend you load 3 shot groups from 70.5-72gr and see how they group without the magnetospeed.
You can also load higher ladder test to look for pressure and see if there is a higher node there. If you do shoot a higher ladder test I’d start at 73,73.5,74,74.5,75,75.5,76. Shoot it at minimum 300 and label or note each shots location. Don’t worry about the magnetospeed yet. Or mount it on a tripod or stand off the barrel.

 

[oregonhuntr]

If you decide to keep going up higher in charges or not I would then identify the velocity nodes you want to keep working with and load in smaller increments. When I preform a ladder test I like to load in .2 gr. increments. For example: 73, 73.2, 73.4,73.6, 73.8, 74. These smaller increments will give you more data points to work with and usually the velocity nodes will become more apparent. It's defiantly more loading and shooting though.

 

[Mike 338]

The term "ladder test" gets thrown around for everything under the sun. That's not a ladder test. Actually, as far as I know, it doesn't have a proper name but your basically shooting consecutive powder charges in search of a flat spot. In this case, your shooting a very light bullet in increments of almost 1%. 1% charges work o.k. in cartridges that use about 30-ish grains. You pack'in bigger medicine. That might work if you were shooting a very heavy bullet but in your case, your velocity spreads are really far apart. I'd do the test again in .2 or .3 gr. increments and just take more shots. I see those 11 shots as inconclusive.

On a real Ladder Test, you'd be shooting at a target at about 600 yards or more and in that case, 1% increments would be appropriate although I'd still go a little less.

 

[Bbear]

Looks more like an OCW test (Optimal Charge Weight). Though your action and brass may not show it, you're about to the top end load on your rifle/cartridge/bullet/powder combination. (The declining velocities towards the high end is one sign of impending over-pressure).
http://optimalchargeweight.embarqspace.com/#/ocw-instructions/4529817134

As for where I'd test, I'd go back and shoot 70.5-72 gr and load three rounds for each one. Allow the barrel to cool off to ambient temp if you can between 3 shot loads. You have a flat spot but shooting 3 loads at each will tell you more.

As I understand a 'true' ladder test, you'd shoot 3 or more rounds of each load at ONE target for each load. The targets would be a minimum of 300 yards. What you are then looking for is where the loads impact poa along a horizontal line.