The present disclosure describes systems and methods for delivering a primer to an operative depth for initiating an explosion of an explosive material in a blasthole. Systems described herein can include a cap structure providing access into the hole and a separable detonator subassembly that can be deployed to convey a detonator to a priming position. Methods of priming a blasthole can include placing such a system on a blasthole collar and deploying the detonator subassembly in conjunction with loading the blasthole with explosive material.