Sig Sauer P320 X-SERIES Full Size Grip Module AssemblySig Sauer P320 X Series Grip Module, Full Size, 9mm . 40 . 357, Large. Install your P320 P250 firing control unit into this Grip Module Assembly to convert your P320 or P250 carry chambered in 9mm, . 357 SIG, . 40 S&W to a Large Full Size X Series pistol system. Requires the 9mm, . 357 SIG and . 40 AUTO slide and barrel. This X Series grip features an extended beavertail and high undercut trigger guard to promote a higher grip along with improved