Some officials taken with the strength and efficiency of the Remington Rolling Block succumbed to the arm’s siren call and, using barrels recovered from U.S. Model 1861 and 1863 rifle-muskets, mated them to Remington actions. The results were promising.
Christopher Miner Spencer became known as one of the greatest gun designers of his age, and his Spencer rifle was eventually fielded as one of the most advanced firearms employed during the Civil War. This is how he got started.
While there are many military rifles that have seen extensive service, the Italian M1870/87/15 Vetterli-Vitali stands out as one of the longest-serving military rifles in any guise.