Hey Denton, How did you arrive at this system? This sounds like it could make my life a little easier looking for the BOSS sweet spot with handloads. As I understand your procedure, plotting centers should give me an ellipse. "From the pattern figure out which BOSS setting will put you out on the end of the ellipse" should I then have 2 settings to work with, one on each side if the ellipse, or am I missing something.
Thanks

I think you've got it pretty well. It's not my system... has roots with Audette and others. The "end" group you plot may not fall exactly on either side of the end, but you'll probably be able to figure out where the end of the ellipse is.



The one thing I may have added to the discussion is that a rifle will print patterns plus or minus 50%, just from normal random variation. If you have a true 1" gun, and you try one BOSS setting and get 5/8", and another, and get 1 3/8", the two settings have produced statistically indistinguishable results. Getting it set right, using the factory instructions is a bear of a job. This converts the problem to finding centers, which is much easier than finding true spreads.



The speed of sound in steel is about 10X what it is in air, so barrel vibrations get to the muzzle before the bullet does. So, by the time the bullet exits, the muzzle is moving.



The muzzle PROBABLY moves in a slender ellipse.



This does two things to the bullet:



1. The barrel points in a different direction at different moments of time. Near the end of the ellipse, it is changing direction the least. So, bullets that exit a few microseconds apart in time end up at practically the same place on the target.



2. The vibration of the barrel imparts a sideways velocity to the bullet. I have calculated this at about 14 fps on the "long" side of the ellipse, and closer to zero on the tip.



Fortunately these two effects are in phase, and produce an effect in the target that looks the same. They just add.



If you can get your bullet to exit right on the "end" of the ellipse, it will be "robust". That means that moderate changes in exit time make very little difference in point of impact.



As I said, there are good physical and statistical reasons why it should work well, but I've never tried it. I just slapped a strain gage on a new rifle that I'm breaking in. I may get a chance to try it this weekend, using powder charge as the variable instead of the BOSS setting.

Could the plotting system be explained in a little more detail? Do I use graph paper or ???. Thanks for your patience with the statistically challenged.

No problem.

Start with several targets, each shot at a different BOSS setting. If you're adjusting powder rather than the BOSS, use different charges. Label each target with the BOSS setting that produced it. While shooting, do your best to maintain constant barrel temperature.

Take a fresh target. On that, plot the centers you got from the separate targets. Label each with the BOSS setting used to produce it. As the settings progress, you should theoretically start to see a small section of an ellipse. Choose a BOSS setting that puts you on the "end" of the ellipse. If the ellipse pattern is not evident, find the two groups where the centers are closer than the others. Choose a setting between those.

I have a WM 338 with the BOSS.Shot an awful load of ammo thru it in the vain attempt to develop accurate loads.
At this stage I simply realized that I was dealing with too many variables,and dont live long enough nor have enough money to try all combinations.
Without BOSS ,its quite a task to find a bullet that your rifle likes,then find the correct powder and powder charge.

Now add the BOSS.Unless you keep the BOSS constant,which sort of defeits its purpose,your combinations are endless.

So my verdict is:if you dont develop your ammo,taking factory f.i. the BOSS might be OK and you might be lucky finding that your rifle shoots that ammo.
But if you are a reloader,its not for me
I just had the BOSS taking off and placed a regular muzzle brake