7.62x51mm NATO is a rimless, bottleneck cartridge originally designed in the United States. It is nearly identical to .308 Winchester. The 149 gr M80 is the same round used by U.S. Army snipers in their M14 rifles. The round is fully jacketed and comes in a brass case. It has a muzzle velocity of 2,790 fps and produces muzzle energy of 2,575 ft/lbs.
5.56mm NATO is a rimless, bottleneck, intermediate cartridge originally designed in Belgium by FN Herstal. It is nearly identical to .223 Remington. The 62 gr M855 is the standard ammunition used by the U.S. Military in the M4 carbine and M249 SAW. The round is fully jacketed and comes in a brass case. It has a muzzle velocity of 3,060 fps and produces muzzle energy of 1,289 ft/lbs.
.300 AAC Blackout
.300 AAC Blackout is a relatively new caliber on the market. It was first produced by AAC in collaboration with Remington. It was approved by SAAMI for retail manufacturer in 2011. It is an intermediate-sized round, between 5.56mm NATO and 7.62x39mm. It delivers the accuracy of 5.56mm with the knock-down power of 7.62mm. .300 AAC Blackout comes in 147 grain and is fully jacketed. It produces a muzzle velocity of 2,076 fps with muzzle energy of 1,406 ft/lbs.
.223 Remington, 52 gr FMJ-BT
.223 Remington, 52 gr FMJ-BT is a full metal jacketed round that is mostly used for hunting. It is nearly identical to the 5.56mm NATO round used by many militaries around the world. It has a weight of 52 grains and produces a muzzle velocity of 3,240 fps. It produces muzzle energy of 1,282 ft/lbs.