ladder testing

[ffwd]

How many of you use ladder testing to find a load.

I had my recently finished rifle to the range to get sighted in and to test H4831 with 168gr bergers.

Weatherby Mark V action, chambered for 7mm Weatherby, 27.5" 1 in 9" Gaillard

Loaded up 17 cases starting at 64gr and going up in .5gr increments until I hit 72gr. I shot same POA on one target. I marked the bullets with coloured ink to differentiate the groups.

I have a few questions.

Should my charges be closer? .2 gr? .3gr?
When do you experiment with seating depth? I'm pretty close to the lands, but I don't have the tools to measure how close.
What should I be shooting off of?

 

[Obtunded]

I regularly use ladder testing.

I usually start with a known empiracle seating depth preference for the type of bullet I am using, for instance, I use VLD bullets, and these like to be in the lands 15 thou. Non VLD's I typically jump 10 thou, and fine-tune after finding a velocity node.

If you want to do things properly, you need a caliper with a comparator. There is just too much variation from bullet-to-bullet to make measuring off the tip a reliable way to measure COAL. One easy way to "find the lands" is to take a fired case and pinch the neck slightly out of round. Stick a bullet into the case mouth and chamber it. Remove the case (Protect the case from being pushed sideways by the ejector) and measure the length.

Do this a few times to ensure that you have an accurate measurement.

This is the lenght-to-lands measurement.

To be honest, to extract the most value out of a ladder test, you need to shoot no closer than 300M, and you need to be a good, accurate shooter. Only do this on a calm day, or early/late in the day when conditions are dead calm and there is no mirage. As to increments, I typically go .2 but I generally know the ballpark I want to be in. With that much case capacity .3 grain increments would be fine.