Well, here ya go then. Have you tested with and without one? I have. Multiple times with multiple rifles, multiple calibers, all high end precision shooting 1/2MOA or better. I too thought there would be a shift in POI due to harmonics. Doesn't appear to be so. 5 rounds with, then 5 rounds without the Magnetospeed, all the rounds as good as I can make them, all the way through various 10 rounds x 10 of each at 0.1gr and 0.2gr increment 'ladder' tests. All at 300-500m under close to perfectly calm shooting conditions. Any FU's were mine. Any 5 shot group POI shift was well under 0.05MOA if I could identify it at all. The tests were performed just to id any problems that the Magnetospeed might introduce. Normally I shoot 10 rounds x 5 or each at my chosen increment.
The Magnetospeed seems to work just fine without causing any problems other than it can be difficult to fit or keep stationary on a few rifles and impossible to fit on others. It needs to be checked to see that it is tight, and not sliding/rotating. Won't work with pistols or full barrel lug revolvers. The descriptions on the Magnetospeed website describe the differences. I bought the V3 when it first came out and I don't think the 'Sporter' was available although I might not have looked carefully. Just a casual glance at the pictures show that the two devices are similar but very different. The Sporter model at $300 looks to be a "light duty' V3. It is shorter, not as deep for accommodating large muzzle brakes, rail has no muzzle blast protection, electronics package is different, accessories look different. It can not be converted with add-on parts, etc. The V3 at around $550 is much beefier and seems very reliable. Mine has around 5-6K shots fired over it and works perfectly. Everything required is included. A 9V battery runs it for days. One item that can be useful to have is a thin piece of bicycle inner tube or neoprene to add under the ballistic nylon strap to provide more gripping area on the barrel.
Labradar can be difficult to set up for reliable cycling/initial id of shot, but once it is dialed in seems to work quite reliably but can still miss a shot from time to time. Main difficulty is discriminating between shots fired by nearby shooters. That can be extremely frustrating. On the other hand, it can be used with virtually any firearm within reason. It is bulky and pretty much requires the base plate accessory or a camera tripod to attach it to. In my terms, it 'eats' batteries, be sure to bring at least a second set of 6 AA or bring a Li-ion battery pack. $750 plus another $60-100 depending on the accessories.
My personal preference is umm, well, about 2/3 leaning towards the Magnetospeed.
That's my mileage.
