.243 Winchester (using Hornady bullets)
Date: Mar 02 2020
The .243 Winchester is easily the most popular of all of the 6mm cartridges. Winchester introduced it in 1955 in the Model 70 bolt-action rifle, but its real history began when gun writer Warren Page created a .24-caliber wildcat based on a .308 Winchester case. This created considerable interest in a small caliber, dual purpose deer and varmint cartridge, and when Winchester commercialized it the demand had already been created, which seemed to almost guarantee its success. Initially it was offered with 80- and 100-grain loads (for varmints and deer, respectively), but today ammunition companies have developed much more versatile loads that have dramatically improved it for both applications. Virtually every major rifle company (domestic and foreign) offers the .243 Winchester as a standard caliber. It offers light recoil, flat trajectory and can be housed in a short action bolt rifle, and always ranks as one of the most handloaded rifle cartridges.
The .243 Winchester is pressure sensitive to changes in components and the accompanying data should not be altered through substitutions. Common mistakes include substituting bullets from another manufacturer of the same weight, or using cases made by another manufacturer. These practices often change pressures, sometimes significantly. If components are substituted, always begin with suggested "start" loads and work carefully toward maximum loads, checking for signs of excess pressure.
Ball powder loads should not be reduced below suggested "start" loads, or pressures, velocities and accuracy can become erratic, and hang-fires may occur. This has also been reported by other labs and is not an uncommon occurrence.
For handloading lightweight bullets weighing 58 through 75 grains, top performing (accuracy and velocity) powders included Hodgdon Varget, H-4895, Accurate AAC-2520, Alliant RL-15, Vihtavuori N-140, IMR-4064 and IMR-4831. Heavier bullets (80 through 105 grains) performed best with slightly slower burning powders such as Alliant 4000-MR, RL-17, RL-19, RL-22; Hodgdon H-4350, Hybrid 100V; Vihtavuori N-160, IMR-7828, Winchester 760 and Supreme 780.