[/align]This late 2004 Sturm, Ruger and Company joined with Hornady to announce a brand-new cartridge. This new .20-caliber round is based on the .222 Remington Magnum case and promises to offer high velocity with low recoil, sharing some common ground with the .22-250 hot rod, as well. The new .204 is currently offered in 32- and 40-grain loads from Hornady, and it looks like an interesting concept right off the bat.
A .20-caliber rifle is nothing new. Walt Berger has been offering bullets for quite some time, and while the caliber hasn't been a household word, I recall seeing a .20-caliber Cooper rifle for sale some time ago at the local Scheels store. The new .204 Ruger is essentially a .222 Magnum case necked down to hold a .204-inch bullet.
Case dimensions are a difficult thing to find so far, but Hodgdon information states that the .204 should be trimmed to 1.84 inches while RCBS says the .222 Magnum should be trimmed to 1.850 inches. Both use the same .378-inch rimless base. The .222 Mag uses a 23-degree shoulder while chamber specs call for a 30-degree angle on the .204. Hodgdon data says the .204 should be loaded with Federal 205M primers while the data for the .222 Mag is based on a Winchester standard rifle primer. Overall load length for the .204 is 2.26 inches while the .222 Magnum is set at 2.22 to 2.28 inches.

Although the .204 is based on a .222 Magnum case, it performs more like a .22-250, using considerably less powder to achieve this high performance. Hodgdon's latest reloading manual suggests that a .22-250 needs 39.5 grains of Varget powder to launch a 40-grain Nosler Ballistic Tip bullet at 4,135 fps while the .204 will launch its lightest bullet, a 32-grain VMAX, at 4,044 fps pushed by 28.3 grains of H335. Hornady's 32-grain .204 load is cataloged to leave a 26-inch barrel doing 4,225 fps while its 40-grain .22-250 VMAX load leaves a similar-length barrel doing 4,150 fps.
The downrange performance is similar as well. With a 200-yard zero both loads are .6 inch high at 100 while the .204 is 4.1 inches low at 300 and the .22-250 is 4.5 inches low. At 300 yards, the 32-grain .20-caliber bullet should be doing around 2,568 fps while the 40-grain .22-250 Hornady slug is doing 2,683 fps or so. The .204 is flatter than the .22-250 all the way out to 500 yards, and I'd suggest that both of 'em run out of steam past that distance, if not before in many applications.