Figuring out what ammunition shoots the best in your hunting or target rifle can be daunting. There are some things you can do to narrow down what will work the best when purchasing a rifle and it has to do with the barrels twist rate.
The barrel twist rate of a rifle refers to the rate of spin in the barrel. My Sako 85 Finnlight II in .308 has a barrel twist rate of 1:11, meaning that the rifling will spin the bullet one whole revolution in 11 inches. The twist of the barrel in a rifle will affect how the projectile travels, as the lower the number means the faster the twist rate.
Twist rate is important when shooting longer distances to ensure that your projectile is stabilised to maximise its ability to overcome air resistance in flight, also known as ballistic coefficient. Each twist rate will have an ideal range of projectile weight to maximise the ballistic coefficient. This is the hard part when looking at 308 projectiles as they range from 100 grains all the way up to 240 grains.
The barrel in the .308 Finnlight II’s 1:11 twist rate meant that a heavier projectile around 180 grain would stabilise the best over distance. As every rifle is little different, the task was to test out a variety of different brands of factory ammunition around that weight range to find what groups the best.
From shopping around gun shops in the area I had a shortlist of available factory hunting ammunition between 165 and 200 grain that would stabilise well and suit medium game. A couple of sessions at the range shooting five shot groups with different brands, I found the Hornady 178gr ELD-X ammunition performed the best with consistently smaller groups. The plastic tip on the ELD-X projectiles ensured the best ballistic coefficient (ability to overcome air resistance) on the way to the target whilst retaining the expansion of a hollow point projectile on impact.
Doing a lot more hunting recently I’m now putting together plans on reloading specific hunting ammunition for the Finnlight. Closely looking at projectiles with a high ballistic coefficient and good expansion on impact.