Since the arrival of firearms, gunsmiths have gone down various avenues in an attempt to supply the operator with a multi-shot solution. In the days of the matchlock, wheellock, snaphance and flintlock, this proved something of an immense challenge though, with the adoption of the percussion-based action, opportunity to bring a multi-shot weapon into existence grew - the "revolver" hand gun being one key solution and popularized by both Colt and Remington. However, during the American Civil War (1861-1865), there proved several multi-shot long guns to be given usable circulation and one of these developments became the Lindsay Model 1863 Double twin-shot rifle musket of 1863. The design emerged from J.P. (John Parker) Lindsay Manufacturing Company of New Haven, Connecticut and attempted to delivered sequential firing of two bullets (ball) through a single-barreled arrangement (Lindsay had lost his brother to an Indian attack and subsequent scalping while defending himself with only a single-shot firearm). Thusly, Lindsay dedicated many resources to the development of two-shot pistols and long guns for such encounters.
Lindsay was able to develop a new method of containing two shots across a single chamber and barrel assembly, the general idea being to have each shot fired in sequence at the operator's discretion by management of two separate hammers (in a side-by-side arrangement). Each charge was loaded down the muzzle of the barrel in the usual way, rammed home by the supplied ramrod, the shots resting in the chamber in the order that they were loaded. With two hammers installed, two percussion caps were required and these were set across two provided nipples. The design only allowed one hammer to ever fall even if both were cocked at the ready, the right having dominance over the left. However, the danger lay when the left hammer was cocked and dropped by the trigger pull, igniting the backload first and sending both charges and bullets into action. The resulting recoil force could prove damaging to the operator or severe malfunction could occur at the action resulting in a complete loss of the rifle and most likely personal injury to the user. The approach proved unique enough to earn itself a US government patent and, when adopted into a serviceable, .58 ball long gun body, the firearm was known as the Lindsay "Two-Shot" or "Double" Model of 1863. It saw only limited action in the Civil War when evaluated under combat conditions by the US Army.
The Lindsay Double Rifle Musket showcased a single-piece wooden body with integrated grip and attached shoulder stock. Three bands were used to secure the barrel to the body with only a short section of the 41-inch long barrel assembly protruding ahead. A ramrod was sheathed in a channel under the barrel for the gun still remained a muzzle-loading weapon at heart, requiring a separate charge and bullet (ball) to be rammed down the barrel. A percussion cap was then affixed to a metal nipple at the action and struck by a pair of cocked hammers actuated by the trigger pull. The trigger was slung under the body within a thin protective ring in the usual way. The right-hand side hammer was designed to always fall first and was easily managed by the firing hand's thumb within easy reach. The action was contained through metal works located at rear of the body. Iron sights were provided at two points - just ahead of the action and at the muzzle - both serving to supply accuracy during long range work. Sling loops at the second barrel band and at the trigger loop allowed the weapon to be transported on march across the shoulders.
The Lindsay Double of 1863 came about at a time that the American Civil War was in full swing so all manner of firearms were in need. The US government actually commissioned for 1,000 of the type with the order dated on December 17th, 1863. However, this appears to be the only order of note for the reach of the Lindsay Double in the Civil War timeframe was extremely limited (the 16th Michigan Infantry being the only recorded users of the type with the guns seeing action at Peebles Farm). In practice, it was found that a poorly-loaded weapon and those operators mistakenly utilizing the left hammer in the heat of battle tended to release both chambers at once with dire results. As such, this particular repeat-fire long gun found few supporters in its time with the Union Army - proving more a flawed, novel design attempt than anything an infantryman could find useful in battle. The weapon eventually fell to the pages of Civil War history while more conventional long guns were sought and ultimately obtained.