Kramer Defense 6.8x45mm Urban Combat Cartridge

By Thomas Murphy

Kramer Defense in Las Vegas, NV, has developed a new cartridge to replace the elderly 5.56 NATO round in use since 1959 when it was named the .223 Remington. It became the 5.56 NATO when FN Herstal in Belgium redesigned the cartridge in 1977 and was designated M855 in the United States. Both the military and law enforcement communities have admitted that the cartridge is lacking in performance when the range is long, or material penetration is required during urban operations.

Larry Kramer, owner of Kramer Defense, has created a new cartridge designated the 6.8x45mm Urban Combat Cartridge (UCC) to improve on the 5.56 NATO’s performance in urban combat situations, where the range is close and short-barreled weapons are employed. It is specifically designed for the M16A4/M4A1/M27/MK18/M249 SAW family of rifles and carbines. It is the same overall length as the existing 5.56 NATO cartridge and can be easily retrofitted to any 5.56 NATO rifle simply by changing the barrel. It uses the same bolt and lower receiver group. The ammunition is loaded with either 110-grain Hornady BTHP-OTM or 115-grain Nosler BTHP .277 caliber bullets. The standard 5.56 NATO cartridge is simply necked up to take the new bullet.

Some of the advantages of the 6.8x45 UCC ammunition include a 38-percent increase in muzzle energy over the 5.56 NATO, and the use of standard military components and packing equipment, stripper clips, insets, and bandoleers. A 300-round combat loadout weighs slightly over two pounds more than a similar loadout of 5.56 NATO. The recoil with the 6.8x45 UCC is 30-percent greater than with the 5.56 NATO, but still well within comfort limits.

Kramer Defense only markets complete upper receiver groups in 6.8 UCC. They have MIL-SPEC chrome-lined bores and chambers, and are finished with a phosphate coating. The upper receivers are made to military specifications with regard to tolerances, fit, and finish. They will drop on MIL-SPEC lower receivers with no modification. To differentiate between the 6.8x45 UCC upper receiver and other caliber uppers, Kramer Defense has notched each side of the standard A2 front sight assembly on their uppers.

The 6.8x45 UCC uses a proprietary 30-round magazine made to MIL-SPEC, and utilizes standard military green followers and springs. The caliber is clearly marked on both sides to avoid confusion with standard 5.56 NATO magazines. Magpul makes a 6.8x45 UCC internally-modified 30-round Gen-3 PMAG that is broached on the interior to remove half of the inside rail that comes into contact with the neck of the cartridge. This allows the larger-necked rounds to feed reliably. These magazines will still feed the 5.56 NATO without problems. These modified PMAGs have been laser-etched for easy identification by the shooter.

The 6.8 UCC and the M249 Light Machine Gun

The US M249 Light Machine Gun is the American adaptation of the Belgian FN Minimi, which first entered service in 1976 and was adopted by US military forces in 1984, and is still in use today. It fires the standard 5.56 NATO cartridge from M27 200-round linked belts. It can be converted to the 6.8x45 UCC simply by changing the quick-detach barrel. The same M27 links will work with the 6.8 UCC and feed reliably Sustained rate of fire is the same as for the 5.56 NATO–85 rounds per minute–without overheating.

Ballistic Performance

Barrel length–10.5 inches

6.8x45 UCC: Nosler 115-grain BTHP
5.56 NATO: M855 62-grain FMJ-BT

This article first appeared in Small Arms Review V21N5 (June 2017)
and was posted online on April 21, 2017


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