Blastshot maker can be filled using petroleum bottles, but only works if a section of pipe is built on the liquid input

Dupes can add petroleum to the blastshot maker using bottles (from a pitcher pump in petroleum). Meaning the required items (refined metal and petroleum) can be added by dupes, without having a liquid input for petroleum.

Even with all the necessary items in the blastshot maker, dupes will not start producing blastshot. The tooltip/mouseover will say "No Liquid Intake"

If you schedule a pipe section to be built on the blastshot maker liquid input, the building becomes functional and dupes start producing blastshot. This is the case even before the liquid pipe is built, and even though there is no petroleum in the pipe.