Originally Posted by
Harry O
Anyway, lets say you have a Bhn 15 mix and are shooting a 20,000psi .38 Special load (midway into the +P region). That is below the yield point so we can divide the pressure by the modulus. That is 20,000 / 2,000,000 = 0.010. This means that you take the original length of the bullet (front to rear) and multiply it by this number to get the length that the bullet will shorten. Lets say that the bullet is 0.700" long (a plain-base .38 Special semi-wadcutter). That means that under 20,000psi, the bullet will shorten by 0.70" x 0.010 = 0.007". It will be 0.693" long while under pressure.