They call it the Mutant because, while it uses a lot of the basic AR platform, both the upper and lower receivers are unique as they were re-sized for the cartridge and to use the AK magazine. In other words, it is not a standard AR by any means though some parts will interchange, like the trigger group, safety, and stock. It does, however, operate much like an AR, other than changing the magazine.

The Mutant answers the need for a more potent weapon than the AR15. Many feel that the cartridge native to the AR, the .223 Remington/5.56x45mm NATO, just doesn't hit hard enough. While the round has dropped many a target over the last 50 plus years, there have been many stories of failures. The round started off touted as an amazing killer in the early days of Vietnam with stories of ripping enemy soldiers into shreds. These effects were usually attributed to the bullet yawing, tumbling, and fragmenting through the target. We later, however, heard stories that it was a failure when it didn't do those things and all you got was a neat .22 caliber hole that didn't impress enemies very much. The failure stories grew as time passed. New loadings, like the M855 with a 62-grain bullet that replaced the original 55 grain M193 load, appeared to fail far more often. Complaints from soldiers in the Blackhawk Down street battle in Mogadishu in 1993 confirmed to many that there was indeed something wrong.

Shortening barrels hasn't helped. The AR originally had 20-inch barrels, but the current M4 has a 14.5-inch one. Even shorter barrels are used for special purposes. Every shortening of the barrel means lost velocity, which reduces the likelihood that the bullet will yaw on impact.

Curiously, according to Army surveys on weapons, while one soldier is very happy with his weapon and ammunition, the next is terribly disappointed. One line of reasoning for this conundrum surfaced in reading about Dr. Gary Roberts' work on the Internet. Roberts is a dental surgeon and Navy Lt. Commander who has spent a lot of time researching wound ballistics. He is a consultant to many governmental organizations and shares some of his work with the rest of us. He noted that while some M4's will stabilize the bullets better than others, some bullets are less likely to yaw on impact. With no yaw, you get a marginal wound.

Another issue has been performance through barriers, such as auto glass. Small, fast, light bullets often end up passing through barriers, and bullet bits don't do much to bad guys. Shooting into cars came up a lot in the Middle East, where the car bomb is a weapon of choice.

Some argue that loading it with the right bullet is the answer, and there has been a lot of research to develop better ones. Some researchers look for bullets that don't need to yaw on impact, while others look for bullets that yaw and tumble reliably. One of the new loads the MK262 with a 77-grain match bullet is used by our special ops troops and anyone else who can get them. While they still have problems getting through barriers, the commentary from the war zones has been very positive on their performance. There are also bullets designed to pass through barriers and still hit hard enough to do damage. These include the MK318 Special Operations Science and Technology (SOST) round with a 62-grain bullet. Reports from the Mideast say that it has been used effectively by Marines in combat and is now their round of choice.