44 Henry round. Henry also supervised a new rifle structure centered loosely to the Volcanic to implement the new ammunition, retaining only the general form of the breech system along with the tubular magazine. This became the Henry rifle of 1860, which was created by the New Haven Arms Business, https://highimpactrounds.com/product/winchester-super-x-20-ga-2-75in-20-pellets-3-buck-1200-fps-5-rd-box/