Labradar consistency day to day?

[cfulback32]

Long version:
I am working up a new load for my AI AT in 6.5 Creedmoor (changing from Hornady to Lapua brass), and my Labradar seemed to read ~30 FPS slower today. The only notable difference was placing the labradar under the barrel today, versus next to the barrel last week. With the same powder charge, same components, same temperature, today was ~30 FPS slower compared to last week. All shots were the first firing on Lapua brass (no prep performed), 140 ELDs, CCI 450s, and charges weighed on a lab scale. Lab scale confirmed with a calibration weight both times. ES for each set of charges is single digit.

I didn't include it in the graph below, but I observed the same thing with my old Hornady brass handload. It is usually ~2730 and ~10 SD, and the few shots I took today were 2,700 (~30 slower). I have always measured to the side of the barrel, but used under the barrel today (not sure if that matters).

Short version:
Does your Labradar give consistent readings from one day to the next with other variables held constant? Do you find placement of the Labradar (side vs under) changes the reading?

Blue dots were charge weight and FPS from last week, red was today:

 

[phlegethon]

Long version:
I am working up a new load for my AI AT in 6.5 Creedmoor (changing from Hornady to Lapua brass), and my Labradar seemed to read ~30 FPS slower today. The only notable difference was placing the labradar under the barrel today, versus next to the barrel last week. With the same powder charge, same components, same temperature, today was ~30 FPS slower compared to last week. All shots were the first firing on Lapua brass (no prep performed), 140 ELDs, CCI 450s, and charges weighed on a lab scale. Lab scale confirmed with a calibration weight both times. ES for each set of charges is single digit.

I didn't include it in the graph below, but I observed the same thing with my old Hornady brass handload. It is usually ~2730 and ~10 SD, and the few shots I took today were 2,700 (~30 slower). I have always measured to the side of the barrel, but used under the barrel today (not sure if that matters).

Short version:
Does your Labradar give consistent readings from one day to the next with other variables held constant? Do you find placement of the Labradar (side vs under) changes the reading?

Blue dots were charge weight and FPS from last week, red was today:

I think this is an interesting question, but you’re never going to find an answer unless you tested multiple positions on the same day, and even then you’d be unlikely to see a difference that was more than the variation between cartridges. If you are checking on different days it’s hard to say that it’s not environmental conditions or the barrel speeding up or slowing down due to wear or fouling.

 

[6.5SH]

Agree with the above on test method.

One thing you can check now though is the individual .TRK files from each session and see if there is a difference in where the radar picked up the shot and how far it tracked it.