A large number of unaltered U.S. M1841 rifles remained on hand in U.S. Arsenals when the Civil War broke out. Primarily those of Whitney's and Robbins & Lawrence's manufacture. To upgrade these rifles, revolver maker, Samuel Colt arranged to purchase 10,500 and adapt them to bayonets and long-range sights. Sight that he affixed consisted of two leaf rear sight he had been using on his revolving rifles, with one leaf flopping forward and one flopping backward from the 100 yard block. Saber bayonet lug he attached consisted of a blued clamping ring with integral .5" long lug attached that could fasten to barrel so the lug projected from the right side. These lugs were numbered both to bayonet and rifle's barrel, the number appearing on lower surface of barrel just behind the location of clamping ring. Colt also bored the rifles up to .58-caliber, leaving some with 7-grooves but re-rifling others with 3 wide grooves. An estimated half of the 10,200 rifles so modified by Colt were of Whitney's earlier production. Due to the Colt association, rifles so modified usually command slightly higher prices than other Civil War adaptations for saber or socket bayonets.