Definitions for ".270 Winchester"
The .270 Winchester was developed by Winchester Repeating Arms Company in 1923 and unveiled the in 1925 as a chambering for their bolt action Model 54The Complete Reloading Manual for the .270 Winchester, Loadbooks USA, Inc., 2004, p.13. The cartridge is based upon the .30-06 Springfield, and the case is slightly longer due to the necking down process.