10 vacuum sealed 20rd boxs of 55gr 5.56 NATO FMJ-BT ammo from PMC Ammunition Manufactured to the exacting specifications required by such organizations and demanded by our customers, X-TAC™ is the choice for the professional and enthusiast alike. At PMC, we know your job demands that you think of everything. But we also know that when the chips are down you shouldn’t be thinking about your ammunition. Battle Packs contain 10 boxes, vacuum sealed together. Technical Specifications MPN 5.56X Bullet Type: FMJ-BT Weight: 55 grain Velocity (feet per second)   Muzzle: 3270 100 Yds: 2898 200 Yds: 2555 300 Yds: 2237 400 Yds: 1943 500 Yds: 1674 Energy (foot-pounds)   Muzzle: 1306 Bullet Path (inches)   Muzzle: -1.50 100 Yds: 0 200 Yds: -2.6 300 Yds: -10.6 400 Yds: -25.6 500 Yds: -49.9 Ballistic Coefficient 0.243 Bullet Length 0.740 Sectional Density 0.156