The following excerpt is from an article that originally appeared on The Firearm Blog Ammunition
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…post was originally published on this site