Primer casing (1) comprising sleeve portion (5) and leading portion (5a), wherein sleeve portion (5) includes tabs (6) to retain primer (11) and blasthole engagement means (2), and wherein leading portion (5a) comprises nose cone (8). Engagement means (2) comprises an array of rigid, multiple projections that are hinged and movable between a retracted position and a blasthole engagement position. Explosive loading hose (13) locales within hose receiving sleeve (7) and can be used to push primer casing (1) into the desired location within the blasthole prior to filling the blasthole with bulk explosive. Methods of loading a blasthole comprising inserting primer (11) into primer casing (1) and positioning primer casing (1) at a desired location in a blasthole are also described and claimed.