velocity lower and wide spread

[FRB6.5]

If you are not shooting at a public range it might be possible to make a box or "tunnel" to place your chrono and lights inside to minimize sun angle and cloud variables. If you search you'll see some rather elaborate setups used with the very long Oehler screens. As Klem suggested going prone for something like this would be best.

Edit:
Some good chrono tips and a picture of what was referred to as a "coffin" at the bottom.
https://precisionrifleblog.com/2012/07/2...liability/