Testing MagnetoSpeed: How Different Positions Affect Point of Impact! 

Now you need to test with the bayonet mounted remotely (not touching the barrel at all) and see if it still moves the impact. This is how I use my MagnetoSpeed and I am very interested in what you find. I've always assumed that since the bayonet was not touching the barrel and I set it about 1/4" below the bullet path that any affect would be minimized or removed. Inquiring minds want to know...

Dont hang it off the barrel, there’s frame mounted options

What happens when you put an additional spacer in the Magnetospeed mount so that its not so close to the barrel? How far down can you move the Magnetospeed to still get a reading and not affect precision?

Let me guess, there is rifling and the bullet has right spin when leaving the barrel. Most probably you witness some Magnus-like effect. As the bullet spins it pulls with itself a boundary layer of air, which also spins with the bullet. This layer hits the side of the magnetospeed creating a high pressure area, which pushes the bullet to the opposite. When the magneto is below, the high pressure area is below and right; when it is above, the high pressure area is above and left; when it is to the left, the high pressure is left and down; etc...

Yes, definitely interesting, and something I’ve never seen discussed before. Many users don’t like the idea of attaching the unit directly to the barrel and there are ways of avoiding that. The phenomenon you’ve evidently identified, though, could affect point of impact even if the unit is attached to the rifle stock and not the barrel. Now I’m curious how far from the line of bullet flight the unit can be positioned and still get accurate velocity readings. As mentioned, perhaps moving it away farther would eliminate the problem.* If not, though, it’s something users of the MagnetoSpeed should be aware of. *According to one comment I found, the offset from the bore line should be 1/8 to 3/8 inch, so that doesn’t allow to move it farther away very much.

I would say repeat the test without the muzzle break. Mine always makes it drop about an inch but I've never put it on the sides or on top.

Very interesting.

How much can you increase the distance to the bullet path to avoid this, without having misreadings?

Y* 0:17 त्त य्य?

POI shift isn't important. Your load development shouldn't be using a chronograph anyway. Let the target tell you what is happening with your load development. Let the size and shape of the shot group tell you what the load is doing. You can have a tighter group with a worse SD and ES, but you keep picking the wrong load because you pick the load with the lowest SD & ES, but yet it won't group as tightly on target. Then when you're done with your load development you can use the magneto speed to record the MV numbers for you ballistic software and you're done. From that point you don't need the chorny anymore.