Caliber .270, bullet diameter .277-inch, is primarily an American phenomenon based on the .270 Winchester, which was introduced in 1925. Its origin is murky; there was an experimental 6.8mm Mauser developed for China so rare that standard references show no photos. No evidence confirms that Winchester was even aware of this obscure cartridge.
Nobody knows for sure why Winchester’s Roaring Twenties engineers settled on that bullet diameter. They probably wanted something based on the .30-06 case that might shoot flatter, kick less, and be almost as versatile. There were other options; both the 6.5mm and 7mm (.264 and .284-inch) bullet diameters were popular in Europe and making inroads in the United States, but in xenophobic post-WWI America, using a “European” diameter might have been out of the question. Continue reading “.270 versus 7mm: Too close to call!”