The Springfield Model 1840 was a flintlock musket manufactured by the United States during the mid-19th century. The .69 caliber musket had a barrel, an overall length of , and a weight of . More than 30,000 were produced by the Springfield and Harpers Ferry armories and two independent contractors between 1840 and 1846 (D. Nippes and L. Pomeroy).
The Model 1840 was a minor improvement over the Springfield Model 1835, and therefore was not dramatically different from the older musket. The Model 1840 featured a longer bayonet with a clasp and a stock with a comb. The designers of the Model 1840 anticipated that the musket would eventually be rifled, and made the barrel thicker than the earlier Model 1835 accordingly. The various modifications to the Model 1840 made it slightly heavier than the Model 1835.
The Model 1840 was the last flintlock musket produced at Springfield and Harpers Ferry armories. Many were converted to percussion lock due to better reliability and weather resistance before they made it to the field. Although produced as a smoothbore musket, most of the Model 1840 muskets had their barrels rifled later, as the designers had expected to fire the newly introduced Minié ball. However, despite having a thicker barrel, the increased breech pressure generated by the new expanding projectile was too great for the conversion process to hold and rifled Model 1840 muskets were rather issued standard .69 caliber round balls.