SAAMI has accepted cartridge and chamber drawings of a couple of new cartridges. Both are Nosler cartridges. One is the recently announced .22 Nosler, which we covered in a separate article. And the next one is a .20 Nosler, which is a cartridge not yet officially announced by Nosler as of today (06/16/2017).
If you remember, the .22 Nosler is a .224 caliber cartridge with a case body similar to that of 6.8 SPC but with a rebated rim of .378 diameter. The case thickness allows to fit the cartridge into 6.8 SPC magazines and the rebated rim makes it fit the standard AR-15 .223/5.56 bolt face. So to switch to this caliber all you need is a different barrel and 6.8 SPC magazines.
Judging by the drawings, the .20 Nosler is based on the same rebated rim case as the .22 Nosler. However, it is not quite a necked down .22 Nosler. If you look closely, you’ll see that it has slightly different shoulder and neck height. Obviously, both cartridges are aimed at the varmint hunting market. The .20 Nosler should be able to offer impressive ballistics for a cartridge fitting into the AR-15 platform. I assume it will be offered with some of the following .204 caliber Nosler bullets:
The most notable of current .20 caliber cartridges suitable for the AR-15 is perhaps the .204 Ruger. Probably, the .20 Nosler will offer a comparable percentage of muzzle velocity increase over the .204 Ruger as does the .22 Nosler over the .223 Remington.
Interestingly, Pacific Tool & Gauge already offers chamber reamers for the .20 Nosler as a new product in their catalog.