I hauled my trusty old Shooting Chrony Beta and my shiny new CED M2 out to my brother-in-law's place along with a Sendero SFII in 7 mag. The Sendero has a Jewell trigger set at 1# 5oz, a KDF Accuracy muzzle break, and a Harris BR-2 bipod outfitted with a Pod-Lok (the Pod-Lok is a nice little accessory). Other than that it's dead stock. I had 10 rounds loaded .010 off of the lands with RE-22. The load data came from the Sierra reloading manual but the bullets were 168 gr Berger VLD's. Per the manual, velocity (for a 168 gr SMK) should have been 2,950 fps. Range was 600 yards with a slight (4-5 mph) 45 degree l-r tailwind. I was using LB 3.0 for initial and followup settings for the scope. The scope is a Leupold Mark IV 8.5-25 x 50mm LR/T. I think that covers the setup.
I set both chrony's up in series, SCB first, at 10' - 12' from the muzzle. I don't have a good spotting scope so I was shooting three and walking down to the target to see how things looked (I got my exercise today). The first three shots were calculated using the book value of 2,950 fps in LoadBase 3.0 (along with actual wind, baro, etc). Going from memory I believe my initial value was 11.75 moa up (100 yard zero)
The chrony's disagreed with one another by about 100 fps.
I've always trusted my good old, solid metal Shooting Chrony and it gave me velocities just under the book value of 2,950 (that rarely happens to me btw) so my initial thought concerning the CED M2 wasn't too good. I walked down to the target to mark the hits. They were low by a good bit. 2 MOA-ish. Ruh roh... it was looking like my SCB was wrong and the new plastic el cheapo looking CED M2 was right or at least closer to right. So... I plugged in the lower velocity info from the CED M2, dialed the scope up 2 MOA per LB3's results, and fired 3 more. This time I was about 2 cllcks (1/2 MOA) high and I needed some wind correction. About 3 clicks if I remember right. Winds were kind of tough (I'm just starting to deal with reading wind seriously) because of a row of trees parallel and upwind of the bullet path plus they were variable from direction and velocity (0 - 5 mph). Downrange the mirage would lay flat at times... others it would be nearly vertical. Follow up shots were within an inch or less of the aim point.
This is my viewpoint of the chrony situation. I think they are both good pieces of gear considering what they cost
. I prefer the construction of the Shooting Chrony. I like the big readout of the CED M2. Obviously I prefer the better data that comes from the CED M2. However- based on bullet drop, I don't think I would bet any money on the validity of it or the SCB's data. Chrony's, imho, at least the lower end ones like these two models, are good for determining SD and ES but the velocity data doesn't seem to me to be on. That said I also have to throw in the possibility that the scope calibration is off. Ie 52 clicks not being equal to 13 moa. So if the scope is off a little and I didn't input something just right in the software, especially considering I had a slight, variable, quartering crosswind, some of, if not all of, the "error" could be attributed to the software and scope rather than the chrony. My guess is that they are all off to some degree.
On another note, the worst group that I had at 600 yards was 6.63" and the best was 2.8". The first group was the worst one and the last group was the best one. The middle group was about 4". I think that, as evening came, the winds died down and that helped the groups out a lot. That and the shooter (me) finally got in the groove and started using good trigger control.
The bottom line for me is that, just like in my work, if you have two measuring devices that don't agree then you have to use an outside method to determine which one is right and which one is wrong. An outside method in the case of my two chrony's was the bullet drop vs velocity data that I had available to use.