It is not a long leap to guess that the pistol's modularity was the reason it got the Army's nod. We said, "From this core, the user can change the grip frame size and color, slide assemblies, and even change to a limited number of chamberings. (The 9mm, 40 S&W, and 357 SIG calibers are interchangeable. The 45 ACP barrel assembly is not.) The grip options are reasonably priced at $47 from the SIG Store. Complete caliber-conversion kits are a pricier at $400.