Handloading Short-Barreled .308 Winchesters
Date: Apr 06 2016
The trend is toward shorter barrels for rifles chambered for the .308 Winchester to increase carrying ease and maneuverability. However, the result is a decrease in bullet velocity from short-barreled rifles, such as the autoloading Colt LE901 with a 16- inch barrel, Ruger Compact with a 16.5-inch barrel and Mossberg MVP rifle wearing an 18.5-inch barrel.
The .308 Winchester cartridge fired from a 21- or 22-inch barrel provides quite acceptable bullet speed for the 40-some grains of propellant it burns. With handloads from a 21-inch barrel it is no problem to reach 2,900 fps with 150- grain bullets with TAC and Varget powders, 2,700 fps with 165s over Vihtavuori N550 and Reloder 15 and 2,600 fps with 180s atop VVN150 and RL-15. A longer 24-inch barrel failed to appreciably increase those velocities.
The .308, however, cannot afford to give up much velocity before it falls to the performance level of the .300 Savage or farther down to the .30-30 Winchester. Bullet speeds from the 16-inch barrel of a Colt LE901 were about 200 to 250 fps slower shooting handloaded 125- to 178-grain bullets compared to velocities produced by 21- and 24-inch barrels. The 7.62 Russian cartridge is similar to the .308, and a test of the Russian cartridge revealed a 306-fps loss of velocity with the barrel of a Mosin-Nagant rifle in its normal 28.75-inch barrel compared to a barrel length of 16.75 inches.
I looked through my .308 handloading records and recorded the velocities of some additional loads to determine if judicious selection of propellants and bullets could lessen velocity loss in short-barreled .308s.
Propellant completely burns within the first few inches of the barrel in front of the chamber. The advantage of a longer barrel is it provides a relatively extended containment of the expanding gases produced by that burning powder to give bullets a sustained push and higher speed. The advice has been to use the same powders that deliver the highest velocities in a long barrel to also yield the fastest velocities from short barrels. That mostly held true for the .308, comparing velocities from various powders paired with 125-, 150- and 165-grain bullets. For example, Nosler 125-grain Ballistic Tip bullets reached their highest speed from a Kelbly’s rifle with a 24-inch barrel with 49.0 grains of Ramshot TAC. The same load had a velocity of 2,908 fps fired from the 16-inch barrel of a Colt LE901, which was the fastest the Nosler bullet traveled from the Colt with three powders.
However, the 125-grain bullets shot from the Colt were only 44 fps slower at 2,864 fps with 51.0 grains of W-748 than the velocity delivered with TAC. The difference, however, was 129 fps between the TAC and W-748 loads fired from the 24-inch barrel. A Mossberg MVP rifle with an 18.5-inch barrel shot the W-748 and 125-grain bullet combination at 2,929 fps, which was a gain of 65 fps for the 2.5-inch longer barrel.
Again, TAC provided the highest velocity of six powders loaded with Sierra 150-grain bullets fired from the short-barreled Colt. TAC also shot the 150 Sierras at the highest velocity from a 24-inch barrel. With 46.5 grains of TAC, 150s reached 2,739 fps at the muzzle of the autoloading Colt’s 16-inch barrel and 2,997 fps from a 24-inch barrel.