I was informed by HK that all HK 93 rifles imported into the US were stamped 223 and they were actually chambered in 223 Wylde.
Here is info from wiki on the 223 wylde:
A .223 Wylde chamber is a hybrid rifle chamber designed to allow .22 caliber barrels to safely fire both .223 Remington and 5.56×45mm NATO ammunition. While the cartridge dimensions of both rounds are the same, 5.56 NATO loads produce pressures in excess of the .223 safe spec. The 5.56 chamber has angular differences that allow higher pressures safely. The .223 can be fired from a 5.56 chamber safely but with reduced accuracy. The Wylde is a hybrid chamber designed to allow both ammunition types to be safely fired with good accuracy.
