Fired at the muzzle, a representative 6.5 Creedmoor load (9.1 g, BTHP, 800 m/s) reaches roughly 319 mm (12.6 inches) into cinder block. That is enough to defeat a typical barrier of this material — treat anything behind it as exposed.
About Cinder Block
A hollow concrete block presents ~50–60 mm of actual material across its face shells.