I finially got a chance to shoot the ladder test with my 300WM that I have been waiting to shoot for a month or so. This test was shot following the setup that is detailed in the ladder test document i have sent to several members here at LRH, with a couple of exceptions.
This test was shot using 220SMKs, and H4831sc, a combo I have used before. What I changed was the seating length, going from .a 3.411" (3.828 on the SP gauge) to a 3.538" (3.955" on the SP gauge). The shorter is a load that I setup to fit in the magazine of my rifle. I started at 65.8gr of powder because I already know that there is another node below this at the shorter length, and because I know this load at this length is safe in my rifle..... no need to waste powder and bullets checking.
It was about 10 minutes before sunset when I was ready to squeeze the trigger the first time, so, as expected, the chrony was blind to the bullets screaming overhead.
I also borrowed the video camera from my brother in law, and set it up about 20 feet from the target at about a 45 degree angle. The camera makes it easier for me to concentrate on breaking the shot, not peering through the spotting scope to find the new bullet hole. its a superior metod compared to using shoot N see targets if you can controll the conditions (as in, not shooting the camera, and not having others around who will shoot it for you.
Here is the layout of the test,
collums are, order of shots, powder weight, Bearing surface length, Expected velocity, actual velocity, and notes.
I used a .3gr step because of the case volume, and I specified the BS length because these are the "oddball" lengths from the sorted bullets. All bullets were uniformed with the meplat uniformer i made myself. If you missed it its over in the bullets and ballistics forum.
Below the rows and colums, is a diagram of my ammo box, and where each round is in the box. Os mean loaded rounds in the box that ae not part of the test.... in this case, the rounds this load will replace, 220SMKs over 73grs of H1000. the Xs are empty spaces. This layout helps me keep track of where I am in the test.
Here is the target.
The numbers are from the left most column. Notice there is no #3. The first two rounds hit where I wanted them, so I didn't need to shoot it. Rounds 1, and 2 were for adjusting the POI and fouling the barrel. After I saw where #2 landed, I decided to exclude #3.
The first thig you will nottice is that there are basically 2 groups, and that the top one is to the left of the lower one. the wind was dying down as the sun went down, so the latter shots did not need the full correction I had applied at the beginning of the test, so they moved left. Further, the horizontal spread is also due to the variation of wind speed. 1mph equates to .5inches of deflection with this load, at this range.
Ill let all of you who are interested take a look at the target, and get some idea where you think you would find the most accurate load before I post back with where I think it is, and what the groups I shot for conformation look like.
I have always been a promoter of the ladder test method of load development, and I believe there is no better way of working up a load.