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Bullet Twist Vs Bullet Weight

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.

Bullet ReloadingIf 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 Rate

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

Progression of Bullets

As the years pass, 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.