We don't have synonyms for blunderbusses yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are blunderbuss.
(n) :
An old style of muzzleloading firearm and early form of shotgun with a distinctive short, large caliber barrel that is flared at the muzzle, therefore able to fire scattered quantities of nails, stones, shot, etc. at short range.
(n) :
An old style of muzzleloading firearm and early form of shotgun with a distinctive short, large caliber barrel that is flared at the muzzle, therefore able to fire scattered quantities of nails, stones, shot, etc. at short range.