Doesn't work on air rifle - Magnetospeed Sporter Barrel Mounted Ballistic Chronograph

Installed the unit on .22 air rifle and could not get a read out despite setting on most sensitive setting. Called manufacturer and found out that this unit will not pick up air rifle pellet, that I would need the V3 model (cost $200 more)to use with air rifle. These kind of limitations should have been spelled out in the product description. Supposedly this will work for a 22LR but I find that hard to believe.