This year I made notes of the chrono reading at ETL and Rivington. More for my own benefit and reference.
BFTA 2 - 765
CB625 - 764
BFTA 3 - 763
CB625 - 755
I set mine to 770 with the CB625 using JSB 8.4s.
If I had remembered at Newbury I would have had 3 as GP1 I could get no reading as it seemed to be stuck?
A club member has the same chrono and it reads 3fps high compared to the CB625. Used a v block to ensure it was level.