The .20 Ferguson Ace is one of a family of wildcat centerfire rifle cartridges based upon the 6mm BR. The .20 Ferguson Ace was probably designed and developed around 2002-2003 by gunsmith and varmint hunter Gaylon 'Ace' Ferguson.
Each cartridge in the Ferguson Ace family shares the same body shape and is necked up and down for calibers from .20 to 6.5mm. The case body is longer and wider than the 6mm BR, has a shorter neck and a shoulder angle of 45 degrees which give it approximately 10% more powder capacity than its parent. This allows higher bullet velocities than an unimproved 6mm BR case. An example round recorded 4220fps with a 40 grain V-Max when fired from a 24" pac-nor 1-11" twist barrel. This performance comes at the cost of the barrel with life expectancy in around 500-600 shots.
.20 Ferguson Ace cases are usually formed from .22 BR Remington stock, then necked down to .204" and fire formed in the custom chamber of the rifle. Major drawbacks are the scarcity of both reloading dies and chamber reamers in this format. CH4D offer dies for the .22 Ferguson Ace.