I have had one of these for years and no problems.

Now that we are scrounging for powers I am working up loads for my 7mm-08 and seem to get some 3 shot groups where one of the groups is off by 100fps on different groups and different days.
Trying H414, H380, Blc(2) and reloader 17 ( a little slow)

Buy a new chronograph or think it is some of the powders?
Thank, JimD

Last 30 years all my guns and family guns shoot H4837 very well so I have not worked up loads in a lot of years until I fell in love with the little 7mm-08 as a fun gun. Any help appreciated.

I also regularly use a Caldwell Chronograph. Your comments do not surprise me and I also find reading differences on different days with the same and known load. I don't think it's powders causing big differences in velocities. In my situation I get velocity differences relative to how bright or overcast the day is. In strong, direct sunlight readings can be erratic with more variance and sometimes the unit shows "error" instead of the velocity. I usually shoot over the chronograph in early morning and know from experience velocities will show a bit slower compared to a bit later in the day. I record all shot velocities and the longer term averaged velocity still works out close to the data info.

Do use the lighted sunshade that comes with the deluxe package With your machine? Thanks JimD

Do you use the lighted sunshade that comes with the deluxe package With your machine? Thanks JimD

quote:

the groups is off by 100fps on different groups and different days.

Too many things change from day to day. unless you are in an enclosed tunnel. and its 72* no wind
Temperature is one of the ones.
how long the round is in the chamber is another.
Wind direction and drag on the bullet.
100' is not that much of a change in impact at 100yrs.
about the chrony if your bullet is not cross exactly at the same point then there can be a difference
I think what you may be seeing is a mixed change of events from day to day.
I dont think you can get a good factual average with only 3 shots.
The first shot out of my rifle across a crony is always lower than the next 9 shots. some times as much as 50 to 75'
Ramble on

Get a LabRadar if you want the best chrono out there.

Try shoot straight through the Chronograph. If your target is a little off to the right or left it will affect the speed. The same for the vertical angle applies.