I would call tech service at Chrony - I just sent mine back today. Been having trouble with mine and lost confidence in it so this last weekend I set my Chrony RIGHT behind a new Oehler 35P of a friend of mine. Oehler was set at 10 feet and my Chrony at 13 feet. Shot everything from a pellet gun, 22LR, 38 spec, 357 mag. 2- 280AI and a 458 through them both at the same time. No matter how it comes back I will be ordering another chronograph and be running them back to back from now on. Really leaning towards getting a CED M2
from here at LRH but sure would like to see one operate first. No one I know is running a CED here in Billings, Mt.