When I was browsing the muzzleloadingforum.com I came across a good post telling how to determine the rate of twist. Most production muzzleloaders gun have this stamped right on the barrel, but some do not. While some people might think the rate of twist is unimportant it really is a very important thing to know about your gun. For example, most inline muzzleloaders will have a twist rate like 1:32, 1:28, or 1:24. In contrast, a production flintlock most likely will have a 1:48 twist. Or, on the far end of the scale a custom built gun it likely to have a much slower twist such as 1:66 or 1:70. What do those numbers mean? Well, the first number, which you probably have noticed is always 1, stands for the rifling in the barrel rotating once 360 degrees. The second number stands for how many inches of barrel it would take for that rotation to happen. Now, not all barrels are longer than the second number meaning the rifling never makes a complete rotation. This causes a problem for someone wanting to measure the rate of twist since just putting a ramrod with a cleaning jag on it down the barrel and pulling it out will not cause it to rotate all the way. This is where the forum post by Birddog6 comes in handy for measuring those short barrels. Below is a modified version of his original post he gave me permission to use.
On a Clean Barrel, push a snug Oiled Patched Jag in to the breech.
Take a piece of electrical tape or masking tape & tape around the rod at the muzzle, bring the two edges of the tape up & pinch together, making a Flag at the 12 o’clock position.
Now slowly pull the rod out (letting the rod rotate) til the flag is exactly at 3 o’clock position.
Measure the distance from the muzzle up to the Flag.
If you pulled it out 12″, take the 12″ times the 4 (as you did 1/4th rotation) = 48, you have a 1 in 48 twist.
If it came out 15″, 15 x 4 = 60, you have a 1-60 twist.
16.5″ is a 1-66 twist
17.5 is a 1-70 twist.
So now that you have measured your barrel’s rate of twist how can you use that information to make yourself a better shot? Well, certain projectiles “like” certain rates of twist. For example, the round ball is most stable at a slow rate of twist such as 1:66. Sabots and conicals on the other hand need much more spin to fly accurately thus they are typically used in barrels with twist rates such as 1:28. That leaves the twist rate 1:48 in the somewhere in the middle between these two projectile types, which means it can shoot both projectiles OK. With practice, trial and error with different loads many people can make these in between barrels shoot surprisingly well, however, it does take some time and work to achieve results. It is possible to shoot round balls in a gun with a 1:28 twist and sabots in a gun with a 1:66 twist, but bear in mind that the load will most likely never be anywhere near as accurate as the correct projectile could be.