I use JSB Exact for Bell Target as well. Simply because its a decent pellet that works well in 95% of the airguns. I use it in all my 4.5mm vintage rifles for bell target.
Easy; that way I cant forget which pellet to use for which rifle
For 10m rifle: RWS R10 for my Walther LG300
My Alfa Proj CO2 Rife : Finale Match pistol
Tau mk300: Daystate Rangemasters/CPs
Tau 200 BT: CPs
Tau mk200 RWS R10

So not all matchrifles prefer flatheads