Rifling is something that today’s shooters take advantage
of, but few know that is hasn’t always been so. Though rifling was invented in
the 1400s, it didn’t become popular until the 1800s. before rifling was widely
used, the barrels of the muskets and revolvers were smooth. This meant that
there was a small space between the musket ball and the barrel of the rifle.
The problem with this design is that it caused the musket ball to literally
bounce off the inside of the barrel, making it impossible to determine at which
point in it’s bounce it would exit the barrel. This made it near impossible to
be accurate with it.
If you look down the barrel of modern guns (unloaded and
broken down, of course) you will see the rifling; a series of grooves laser cut
into the barrel in a circular fashion. Rifling is described by what is called
its twist rate. The twist rate simply tells you how far the bullet must travel
before it makes a complete rotation. For example. The twist rate might be 1:12,
meaning that the bullet will make a complete rotation in 12 inches. The shorter
the distance, the faster the twist rate, meaning the faster the bullet will be
spinning when it leaves the barrel.
The twist rate of the barrel, along with the bullet’s
length, shape, and weight all have an impact on accuracy. However, we are going
to look at the correlation between bullet weight and bullet twist.
Finding the Twist
In order to find the right bullet weight for your gun, you
first need to determine the twist rate of your barrel; heavier bullets will
need a higher twist rate to get them moving fast enough to stabilize through
the air. Finding the twist rate is easy.
Using a cleaning rod, place it into the barrel until the
other end comes out of the breach. Now, secure a tight-fitting patch on the
cleaning rode and then place a piece of scotch tape, or masking tape, around
the cleaning rod at the point it exits the barrel. Place a dot on the tape.
Now, once you slowly pull the rod out of the barrel, watch the mark on the
tape. When that mark makes a complete rotation, Measure the distance between
the mark and the end of the barrel; you now have your twist rate. If it’s
10-inches, your twist rate is 1:10
As the years as passed, the construction of bullets has changed.
For example, in the Civil War, Muskets like the 1861 Springfield would fire
heavy lead bullets at a twist rate of 1:78 with exceptional accuracy, while
today’s AR-17 can fire as fast as 1:7 with the longer, modern bullets. While
the slower twist rates can cause the bullet not to be as stable through the
air, with a fast twist rate and light bullet, you can over-stabilize the
bullet, causing it to go off mark as well.
For re-loading the perfect round, this can be a complicated
process of trial and error. While matching the proper bullet weight with the
twist in your rifle won’t guarantee absolute accuracy, it will ensure that the
bullet flies through the air as stable as possible, allowing you to fine tune
other aspects of your process for accuracy. In the end, remember it is better
to have too mush twist than not enough.