The 338 CJMK (Crowley-Jones Mastodon Killer) was developed by JD Jones during the early silhouette shooting days and was based on the 35 Remington case neck down, with fellow shooter Phil Crowley building the first Remington XP silhouette pistol for it. According to JD Jones, their local range had a steel mastodon target at 250 yards which no one could bring down until the 338 CJMK arrived on the scene. See also COTW Vol.6 p.204.
