This is a discussion on magneto speed within the Product Review Requests forums, part of the SniperForums.com & SniperCentral.com Related category; how much poi change for 308...
how much poi change for 308
Unless you plan on shooting in the field with the Magneto speed attached what difference does it make. Most people I know with Magneto speeds, that use them while working up a load, just shoot and evaluate the groups they get with the M/S attached and when done make the necessary adjustments in their zero with their sighter shots.
FWIW, the POI shift will be different on every barrel so as Rhyno430 said "Depends".
Are these more accurate than conventional chronos or just more convenient?
Second, distance between sensors has an effect. The magneto speed has closely spaced sensors. Compare that with the "Gold Standard" of the chronograph world, the Oehler 35 that has several feet between sensors as well as a third sensor to validate the first set of readings (Much like one would use two stop watches to get a closer time reading in a race (or even the old fashioned speed "clocking" from the air by State Troopers).
The closer the sensors the faster the computer clock speed.
Now for the real question, is the Magneto Speed "Accurate Enough". Sure seems to be but if you want to get the most accurate, consider one of those 8' long Oehler's.
Yes, the Magneto Speed wins for convenience but I've never found it to be a hassle setting up my Pact. I just use it after all load development is done then I'll shoot a practice session over it, at least 25 rounds or more, so I have a good handle on the speed, ES/SD.
The Magnetospeed Sporter is $179 and as long as you don't have a suppressor or gigantic brake, it mount's easily to the firearm and unless you really mess up it's hard to shoot. The Shooting Chrony is $139 for an acceptable model and those of us that have used them know that set-up is not simple and shooting them is fairly easy if you are not paying attention. They do have their drawbacks but I prefer them to traditional chronographs for their ease of use and their accuracy.
OP, to your original question about the POI shift, I had a 2.5Mil shift toward the 2 o'clock and groups opened up from .3-.50MOA to 1.5-2MOA.
As for setup, if one uses a chamber type laser bore sighter, sights the rifle on the target and secures with adjustable rest, on bipod, and rear sandbag, setup is about as long as it takes to put the tripod in place and line up the dot over the sensors. No need to run back and forth or have a helper guide you into position.
I don't have any issues with magnetospeed chrono's and for those that want them just remember that they too have their setup issues with strap,shim/spacers, alignment with bore, etc. Then there's the issue of suppressor or huge brake.
What's interesting is the number of chronographs in a market that was once limited to people who only hand deeper pockets than most. Now you can buy a "Fold -a - Box" Chrony off most bulletin boards for ~$50. I use one for "Downrange" speed measurements when I want to do my own BC Calc's.