Over a period of time I?ve heard a lot about the selection of a barrel twist for a smokeless muzzle loading rifle. The debate has been fueled by articles in magazines and web pages that offer one solution or another to the twist equation.
The most commonly heard twist theory says that too tight a twist was a common error in early in-line muzzle loaders and has tried to rein things back to the point of saying that optimum accuracy will not be had unless the barrel twist is less than 1 in 26 inches.
There is logic to that conclusion but I must say it is true in only a limited sense. Sure best accuracy may be had in a BP or sub shooting rifle with a slow twist but there is a reason for this, a reason that has much less effect when shooting smokeless powder.
If you shoot BP the speed of the projectile is limited. From minimum to maximum load level may only be a 150fps or so. That is especially true when you consider most everyone wants the highest velocity possible so tuning is often restricted to near the maximum charge level. Because of the slower speeds and moderate tuning ranges it?s easy to see rifling twist may have considerable effect. It is a classic arrangement where the fuel does not have enough range for the rifle so we tune the rifle to the fuel.
On the other hand shooting smokeless a great many bullet speeds are possible and every one of them is well beyond BP or sub capabilities. I?ve shot the common 250 grain bullet used in a 50 caliber sabot to as little as 2050fps and as much as 2750fps from the same smokeless rifle. That?s quite a range and offers quite a number of tuning possibilities.
All the bullets in this picture are shot in a muzzle loader except the 30 caliber bullet on the far left. What determines the needed twist for each bullet is the length. The heaviest bullet is on the far right however because of its' stubby construction it needs the least twist to shoot accurately. The longer bullets need more twist so selecting a twist requires knowledge of the bullet to be shot. The bullet that needs the most is the 30 caliber bullet on the far left. It is not the longest but it is thinner so it is the longest compared to caliber.
One may ask, why is twist an issue in the first place? I don?t think it really is, however it can surly be on a great many shooter?s minds because what might happen in different firearms is a mystery. What I mean by that is you can theorize all you wish but the only way to know for sure is to shoot. It has been only recently that I could compare two twists in the same caliber together.
The two twists I?ve used are 1 in 28 and 1 in 22 inches. To get started I also enlisted the help of Dave Daub. Dave has a similar set of rifles and barrel twists as I have he is also able to shoot often and at ranges to 300 yards. Using our combined results over the last 10 months I think it s safe to conclude it would be very difficult to ascribe any accuracy advantage to a slower twist.
In the tests ran so far (in 45 caliber) the 1 in 22 barrel is more accurate, however since the sample size is only two rifles for each twist that could be seen as having two more accurate rifles rather than an advantage. What is certain is the faster twist has very little if any noticeable effect of accuracy when fired from a smokeless rifle. When Dave and I both can produce near 1 MOA accuracy at 300 yards with sporting rifles accuracy is without question. Most groups of three averaged 1.2 to 1.3 MOA when firing sabots. I?ve seen greater accuracy (but at this point only at 200 yards) when shooting sabot-less projectiles.
When using smokeless there are so many possible adjustments and bullet speeds the load can find an accurate place to settle. That being the case it can be said that within the limits of +6 and -4 any twist near 1 in 26 should work extremely well. What this means to the shooter is one less thing to worry about. In fact it could be said that the selection of a quality barrel is more important than an exact twist.
It still remains a mystery what even faster twists might do when shooting bullets of the same sectional density as now used. However I have a method to figure something out about that as well. Currently I?m assembling a rifle capable of shooting a 40 caliber bullet in sabot-less configuration. This barrel twist is 1 in 16 inches. It should not be terribly long before some results are available. I know that since there will be no sabots used results will not be directly transferable back to a larger caliber but I am anxious to see what can be done with this very fast twist in a smokeless muzzle loader.
The most commonly heard twist theory says that too tight a twist was a common error in early in-line muzzle loaders and has tried to rein things back to the point of saying that optimum accuracy will not be had unless the barrel twist is less than 1 in 26 inches.
There is logic to that conclusion but I must say it is true in only a limited sense. Sure best accuracy may be had in a BP or sub shooting rifle with a slow twist but there is a reason for this, a reason that has much less effect when shooting smokeless powder.
If you shoot BP the speed of the projectile is limited. From minimum to maximum load level may only be a 150fps or so. That is especially true when you consider most everyone wants the highest velocity possible so tuning is often restricted to near the maximum charge level. Because of the slower speeds and moderate tuning ranges it?s easy to see rifling twist may have considerable effect. It is a classic arrangement where the fuel does not have enough range for the rifle so we tune the rifle to the fuel.
On the other hand shooting smokeless a great many bullet speeds are possible and every one of them is well beyond BP or sub capabilities. I?ve shot the common 250 grain bullet used in a 50 caliber sabot to as little as 2050fps and as much as 2750fps from the same smokeless rifle. That?s quite a range and offers quite a number of tuning possibilities.
All the bullets in this picture are shot in a muzzle loader except the 30 caliber bullet on the far left. What determines the needed twist for each bullet is the length. The heaviest bullet is on the far right however because of its' stubby construction it needs the least twist to shoot accurately. The longer bullets need more twist so selecting a twist requires knowledge of the bullet to be shot. The bullet that needs the most is the 30 caliber bullet on the far left. It is not the longest but it is thinner so it is the longest compared to caliber.
One may ask, why is twist an issue in the first place? I don?t think it really is, however it can surly be on a great many shooter?s minds because what might happen in different firearms is a mystery. What I mean by that is you can theorize all you wish but the only way to know for sure is to shoot. It has been only recently that I could compare two twists in the same caliber together.
The two twists I?ve used are 1 in 28 and 1 in 22 inches. To get started I also enlisted the help of Dave Daub. Dave has a similar set of rifles and barrel twists as I have he is also able to shoot often and at ranges to 300 yards. Using our combined results over the last 10 months I think it s safe to conclude it would be very difficult to ascribe any accuracy advantage to a slower twist.
In the tests ran so far (in 45 caliber) the 1 in 22 barrel is more accurate, however since the sample size is only two rifles for each twist that could be seen as having two more accurate rifles rather than an advantage. What is certain is the faster twist has very little if any noticeable effect of accuracy when fired from a smokeless rifle. When Dave and I both can produce near 1 MOA accuracy at 300 yards with sporting rifles accuracy is without question. Most groups of three averaged 1.2 to 1.3 MOA when firing sabots. I?ve seen greater accuracy (but at this point only at 200 yards) when shooting sabot-less projectiles.
When using smokeless there are so many possible adjustments and bullet speeds the load can find an accurate place to settle. That being the case it can be said that within the limits of +6 and -4 any twist near 1 in 26 should work extremely well. What this means to the shooter is one less thing to worry about. In fact it could be said that the selection of a quality barrel is more important than an exact twist.
It still remains a mystery what even faster twists might do when shooting bullets of the same sectional density as now used. However I have a method to figure something out about that as well. Currently I?m assembling a rifle capable of shooting a 40 caliber bullet in sabot-less configuration. This barrel twist is 1 in 16 inches. It should not be terribly long before some results are available. I know that since there will be no sabots used results will not be directly transferable back to a larger caliber but I am anxious to see what can be done with this very fast twist in a smokeless muzzle loader.
