1211171649a January 1, 2018 at: 1500 × 844 In: BIG Freakin’ Cartridge Test 006: PMC XP193 5.56x45mm 55gr FMJ, 16″ and 20″ Barrels ← Previous The 20″ configuration used for velocity testing, shown here with the IMI 77gr Razor Core load that was the subject of two earlier articles.