You cannot double-tap with a muzzleloader.
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I was under the impression you COULD reload.
First, the term double tap means pull the trigger twice with a semi automatic weapon,
and second, in the time it takes to reload a muzzleloader, the buck has charged through the underbrush and you don't have the shot anymore. Especially if it wasn't a kill shot.
Disclaimer: I have never hunted but I pay attention. My late father-in-law was an avid deer hunter, even in the muzzleloader season. Whenever he said "My Deer", he was not talking to my mother-in-law, he was talking about his trophy in the den.