A very good read on the 20 caliber offerings versus .223 and .22-250.
http://www.6mmbr.com/20Caliber.html
Here is an excerpt:
"I'm often asked how a 20-Caliber gun compares with the ever-popular .223 Rem. Well, I tell people the Twenty is flatter-shooting, easier on barrels, and it is a better choice for small varmints, whether you want to "mist 'em" or save the pelt.
The Velocity Edge--A .204 Ruger drives a 40-grainer 600 fps faster than a .223 Rem can push the typical 22-Caliber 50gr bullet. This higher velocity produces a flatter trajectory. Additionally, grain for grain, 20-Caliber bullets have higher ballistic coefficients than .224 bullets. Combine this with the extra velocity of the 20-Caliber, and you get superior performance in the wind. Run the numbers and you'll see--a 40-grainer shot from a .204 Ruger has less drop AND less wind drift than a 40gr or 50gr bullet fired from a .223 Rem. You'll find the data in the chart below.
Component Economy and Barrel Life--All the Twenties burn way less powder than a 22-250, and the smaller Twenties use less powder than a .223 Rem. This attribute actually has two advantages. First, it makes shooting 20-Caliber cartridges more economical, but mostly it means less barrel heat. A typical varmint hunter may shoot several hundred rounds in one day, so barrel heat is an important issue.
Terminal Ballistics--For hunters seeking maximum explosive effect on a small varmint, Twenties deliver the goods. Because it passes through the rifling much more quickly, a 20-Caliber bullet will be turning much higher RPMs than a 22-caliber bullet launched from a barrel of similar twist rate. Experienced varminters will tell you that high spin rates create the most explosive impacts. On the other hand, if you shoot a non-fragmenting bullet, the Twenty can minimize hide/fur damage. If you plan to keep the fur, you want the smallest possible hole or damage to it."
From a personal experience, I have switched over from .223 to .204 for varmint hunting. I saw the light when P-dog shooting this past June with THR forum member Lunde. I saw him have a 92% hit rate at distances out to 338 yards. My .223 worked well but for pure explosiveness the .204 made the P-dogs absolutely erupt. It was as Lunde alluded to...it made a large WHAP sound when striking a P-dog. I didn't even have to watch his shots any longer to know if he had a hit.....I could just listen and tell. I thought on a breezy day that the 50 gr V-Max .223s that I was shooting would easily outperform the 32 gr BlitzKing .204s. That just wasn't the case.
Flat shooting, fast, explosive, less barrel wear and tear, proven in the field, more rifle companies offering this caliber......it isn't going away anytime soon..
My new Cooper Montana Varminter in .204: