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Originally Posted by Unclenick
Just watch out for muzzle blast causing false triggering if you use the air rifle clamp. You may want to pull that off and back up a bit. SAAMI numbers are taken at 15 feet from the midpoint between screens.
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This is certainly a concern, and may result in the thing being returned.
There is only ONE LED emitter for each sensor, so I tend to think that the reason for clamping the thing to the muzzle is because the muzzle needs to be pretty well aligned with the axis of the two emitters. Backing off even a little bit could result in being off-axis -- especially with a handgun.
The problem you describe is quite real. Many years ago, I set out to quantify velocity loss in .45 ACP as a result of barrel length. I put together four Para-Ordnance pistols, a P14.45 (5" barrel), a P13.45 (4-1/4" barrel) a P12-45 (3-1/2" barrel) and a P10-45 (3" barrel). I was using an indoor range, with a CED Millennium chronograph set up 10 feet from the firing line. All went well with the 5" barrel for establishing the baseline muzzle velocity.
Once I switched to the Commander-length (4-1/4" barrel), things started to go off the rails. I was testing eight different brands and lines of ammo. With the P13-45, 185-gr Speer Gold Dot produced an Error reading on the chronograph. When I switched to the P12-45 (3-1/2" barrel) I got errors with the Speer Gold Dot and with 185-gr Federal Personal Defense. And when I tried the P10-45 (3" barrel) in addition to those two I also got errors with 230-gr Independence FMJ.
Moving the chronograph out from 10 feet to fifteen feet removed the errors.
Consequently, I will be curious to see if this little toy will work with rimfire ammo. I hope so. The CED Millennium is a very nice chronograph, but using it at the indoor range means being there on a day when they're not busy, so the owner can shut down the left side (there's a 12-inch concrete wall between lanes 1-6 and lanes 7-12) to allow me forward of the firing line to set it up and run the umbilical cord back to the shooting bench. It's even worse at the outdoor range of my shooting club, because setting it up and making any adjustments requires waiting for a break in shooting before I can venture forward of the firing line.
If this thing will work, it will be much more convenient. But I very much regard it as an experiment.
As an alternate, I'm also considering this one:
https://www.amazon.com/dp/B0C2GX62QS...hk_typ_imgToDp
Some reviewers have commented that it works with 9mm, so I hope it will also work with .22LR.