poor swing; hanging back during the swing
Golf idiom: a swing where the body hangs back, lacking forward weight shift, likened to an old-fashioned cannon. Literally 'Meiji-era cannon'.
His swing is a 'Meiji-era cannon'—he doesn't get much distance.
From the image of a Meiji-era cannon that recoils backward, describing a golf swing where the body hangs back instead of shifting forward.