A more specific example 298, MkIVb is listed as having x2 #152 .303 Bren CMGs.
It should have #117 0.5 Vickers TMG
And
#137 Vickers T/CMG
The 15mm BESA should probably have similar if not better penetration as the .55 boyes.
From
Tony William's site.
METRIC DESIGNATION 15 x 104/101
RIM DIAMETER - 24.9 mm
NATIONALITY - CZ / UK
PROJECTILE (type/weight) - AP / 75 (grams?)
VELOCITY - 880 (m/s)
NAME / WEAPONS - WW2 ZB vz/60, BESA afv