Smokeless powder can cause serious injury if used in a muzzleloader.

Direct answer

The kind of powder that can cause serious injury (including blown barrels and loss of fingers) when used in a traditional muzzleloader is modern smokeless powder , rather than black powder or approved black‑powder substitutes like Pyrodex.

Why smokeless powder is so dangerous in muzzleloaders

  • Smokeless powder generates far higher pressures than black powder for the same volume or weight, which a conventional muzzleloader barrel is not designed to withstand.
  • Using smokeless powder in a muzzleloader can cause the barrel to rupture or “explode,” turning it into a pipe‑bomb‑like failure that can seriously injure or kill the shooter or bystanders.
  • Safety training materials and hunter‑education guides explicitly warn: only black powder or approved substitutes should be used in muzzleloaders, and “smokeless powders can cause serious injury if used in muzzleloaders.”

In short: a traditional muzzleloader should be fired only with the correct grade of black powder or a manufacturer‑approved substitute—never with smokeless powder, even in small amounts.

Safe practice reminder

  • Use only black powder or labeled black‑powder substitutes specifically approved for your firearm.
  • Follow your muzzleloader manufacturer’s manual for powder type and maximum charge.
  • If you are ever unsure what powder you have, do not load or fire it; treat unlabeled or “rebottled” powder as unsafe.

TL;DR: The answer to “what kind of powder can cause serious injury if used in a muzzleloader” is smokeless powder, which should never be used in conventional black‑powder muzzleloaders.

Information gathered from public forums or data available on the internet and portrayed here.