RIFLE: AERO PRECISION MODEL TR15 THUNDER RANCH RIFLE, SERIAL NUMBER TRO 4378, BLUE / CCH, CASE NOT INCLUDED, SEMI - AUTOMATIC, 5.56 NATO, 16" Notes: Aero Precision TR15 Thunder Ranch 5.56 NATO Rifle. Comes with one 10rd magazine. Barrel: 16", 4150 chrome-moly, 1:7 twist Gas system: Mid-length Receivers: Forged Aero M4E1-based lower and slick-side upper Handguard: Aero Atlas S-One M-LOK Furniture: Magpul MOE grip and SL stock Muzzle device: VG6 Delta Trigger: ALG Defense mil-spec trigger