What is the bullets bearing surface?

The Bullets Bearing Surface (BBS) is that portion of the bullet which comes into contact with the rifling of the barrel.

The bullets bearing surface has a direct impact on the pressure level generated inside the barrel.

This is how we measure the bullets bearing surface

We use these two methods to measure the bullets bearing surface

  1. Using two bullet comparators of the same caliber attached to a caliper
    1. Attach the two comparators to your caliper making sure they are precisely aligned.
    2. Zero your caliper.
    3. Insert the bullet, make sure that the bullet fits snugly between the comparators so that there are no play.
    4. Add the measurement to the load test, or your recipe.
  2. Using fine grit sand paper
    1. If the bullet have enough flat surface you can lay the bullet down on its side on top of the sand paper.
    2. Move the bullet gently backwards and forwards until there is a visible area where the sand paper came into contact with the bullet.
    3. Measure that area and add it to the load test, or your recipe.

TIP: Repeat the steps above a couple of times to get an average for better results in your load test.