Hi just a few comments after coming back to this topic after a few weeks more testing with various chronographs.
Firstly Bryan Litz's articles on chronographs was a great read
http://www.appliedballisticsllc.com/Art ... hapter.pdfBut a few things concerned me that I would like to point out to the readers. Firstly the very poor results from the PVM. We have had 3 of these units up here and find them quite good but it is important to set up correctly and with shot placement through centre of screen. When I looked closer into Bryans results I saw he actually did get very good results in position 3 (figure 15.15) with a st dev of errors against the Oehler of 1.6 and 1.1 for each unit respectively - that is assuming no error with the Oehler which is incorrect so some part of this variation would be coming from the Oehler unit - relatively speaking if these units are set up in the correct area then they are very consistrent shot to shot. Looking at his set up with all in a row it is not hard to see why if he place shots in the top left and right corners of the screen by trying to achieve positions 1,2 in the triangular frame then the shots may have been outside the optimal reading area for these chronographs. Whilst Our testing would concur with Bryans that there is some difference between the reading on the PVM and others such as the Magnetospeed (around 20 fps in our case) the accuracy for shot to shot testing of sd can be very good.
The labradar seems capable of very consistent readings too. Those chasing ultra low SD (say <6) may find it nigh on impossible to achieve decent consistent results with a lot of brands due to the sampling errors of the chronographs swamping the true velocities and need to do this type of testing with some of the better brands. Oehler, PVM, Labradar etc.
Magnetospeeds are great. Highly portable, Not reliant on light and can be used to get a relative velocity measurement consistently with a relative degree of accuracy but do not expect them to measure down to ultra low sd when you are chasing that final fine velocity spread.