Thanks for all the great conversation it was stated you can't shoot groups with the magno something about change of point of aim I understand the weight of it will change POI will it be a consistent POI or will it be all over the target please explain
The MagnetoSpeed [as designed] attaches to the muzzle end of the barrel. The unit physically has weight, and so it can act somewhat like a barrel tuner; which is basically an adjustable weight attached to the end of the barrel. In other words, attaching the MagnetoSpeed to the barrel changes the barrel harmonics, possibly altering or interfering with the interpretation of you're actually trying to measure (precision). This is why many have switched over to the LabRadar; it does not physically contact the rifle.
I have both units, I use the LabRadar. I purchased one of the very first MagnetoSpeeds available and used it for several years before switching. The MagnetoSpeed is very accurate and very reliable. I'm not sure I ever dropped a shot velocity while using it. The main issue with it is that by acting somewhat like a barrel tuner, it can affect group size and shape. When doing load development using the MagnetoSpeed, I would load 10 rounds at each charge weight/seating depth/etc. I would shoot 5 of each for velocity, then come back and shoot the other 5 for grouping. For that reason, I have looked at hundreds, if not thousands of groups representing the same loads that were fired both with the MagnetoSpeed attached and not attached. Having the unit attached can affect both size and shape of the group. However, I never found the effect to be predictable. Sometimes the groups fired with the unit attached would be larger, sometimes they would be about the same, sometimes they would be even smaller than with the unit not attached. Nonetheless, there can be a noticeable difference in group size/shape having the unit attached versus not attached. The magnitude of the effect likely depends on the barrel contour/length and the specifics of the load (i.e. like a tuner effect on barrel harmonics as it is screwed in and out).
The other issue readily noticed is the change in point of impact (POI). After doing many experiments back when I first received my new MagnetoSpeed, I reached the conclusion that muzzle blast off the sensor deck of the unit is the most likely cause of this effect. What it really means is that your shot POI might print higher on the target with the unit attached than without. Not a big deal, really. That's why rifle scopes have elevation turrets. Because it's unlikely that the MagnetoSpeed will ever be attached in
exactly the same position on the barrel during successive use with manufacturer's attachment system, the increase in POI and/or change in group size/shape may not be the same every time you use the unit. That is a big part of the reason people have figured out other ways to attach the MagnetoSpeed to the rifle in such a way it doesn't impact barrel harmonics (i.e. spigot mounts, etc.). The fact that anyone felt the need to do this tells you a lot, IMO.
Regardless of what type of chrono you buy, none are "perfect". Most are capable of providing useful and accurate velocity data. Some are a little harder to set up, but relatively inexpensive. Some are really easy to set up and use, but are pretty pricey. Others fall somewhere in between. Writing down a few "must have" features and setting an absolute top price point you are willing to spend may make it easier to reach a decision.
