The importance of rifling
by Tom Gaylord
Writing as B.B. Pelletier
This report covers:
- Kentucky rifle
- The smoothbore rifle
- How accurate?
- How I know
- How they did it
- The point
Reader Fido3030 inspired today’s report. He is intrigued with the accuracy of an unrifled BB gun — let’s use the Daisy 499 as an example. At close range we know that the 499 has accuracy that is unparalleled. The gun is made for the Daisy National BB gun Championships and is so accurate that other models don’t even compete. The competition distance is 5 meters, which is just over 16 feet. At that distance, this gun will keep all its BBs in the 10-ring of the target.
But increase the distance to 10 meters, which is twice as far, and the BBs start to open up. There is a limit to how far a round ball will remain accurate. Fido said he thought the ball was accurate because is equalized the air pressure on all sides, being smooth and spherical. That seems to be right for a short distance, but after the ball has flown farther it seems like the air starts working some mischief.
I told Fido that the Kentucky rifle was what proved the value of spinning the ball. Daniel Boone is recorded to have intentionally hit a man in the head at 200 yards with a shot from his Kentucky rifle. Fido responded that he thought that many Kentucky rifles were smoothbores.
I’ve heard that the majority of Kentucky Rifles were actually smoothbore. In the woods they were accurate enough to hit a deer at the distances they could see one, but could also pattern a small load of shot. I think this is from the Dixie Catalog.
The reason you may have read this is because many of the old Kentucky rifles are smoothbores today because they were shot out. When that happened, it was common practice to bore them out smooth or to re-rifle the barrel to a larger caliber. Boring smooth was cheaper and a lot of the old guns became shotguns at that point. And that leads me to the next point.
The smoothbore rifle
Smoothbore rifle sounds like a contradiction in terms. Like a square circle. And the majority of people who use the term rifle today do not use it correctly, or even know what it means. They use it when they really mean long gun. A gun is not rifled — a rifle is. Does that make sense? But smoothbore rifles do exist. If the gun has a front and rear sight and if the barrel walls are thick, it probably started out as a rifle.
In the middle 1800s a group of shooters in Ohio was shooting at paper targets with smoothbores that had once been rifles. They were interested in seeing how accurate such guns could be.
The difference between a shotgun that was made to be a shotgun and a smoothbore that was once a rifle is the thickness of the barrel. Shotgun barrels are thin, where rifle barrels are thick. I have seen a rifle with a smooth bore that had a barrel of almost two inches in outside diameter. The walls of the barrel were over a half-inch thick at the muzzle! Not only did this gun start out as a rifle — it was an extremely heavy bench rifle made for target shooting only. But it was shot out and then bored smooth, turning it into a gun called a smoothbore rifle.
The muzzle of the Nelson Lewis combination gun shows the relative thickness of a rifle barrel (right) to a shotgun barrel. Even though the rifle bore is much smaller in diameter, the barrel walls are thicker to take the additional pressure of the powder charge, plus the ability to be re-rifled when it is shot out.
Kentucky rifles and the rifles that followed used a round ball inside a tight-fitting cloth patch. These patches wore the iron of the rifle barrels very fast. You might get 5,000 shots before the rifling was worn smooth. While that sounds like a lot compared to what a centerfire rifle gets today, it is nothing compared to what a rifle will get if it shoots lubricated lead bullets. They can get upwards of 30,000 shots, and rimfires that shoot lead bullets will get close to 100,000 shots before the barrel is worn out. So by comparison the patched barrel is rough on rifling.
Before patched balls, there was no rifling to watch, so nobody paid much attention to how many shots a gun could give. The wear-out rate was probably equivalent to that of rifled barrels, but it wasn’t talked about as much, as far as what I have read.
So how accurate were these smoothbore rifles? Well, it’s been at least 15 years since I read about the Ohio shooters and all my attempts at research have run into a dead end. I did find a guy on a muzzleloading forum who was claiming to put 5 round balls from a smoothbore into 2 inches at 50 yards today, so I would assume the shooters in Ohio were at least that good. They were probably better.
Out at 100 yards, though, the accuracy drops off. If they could shoot 5 shots into one inch at 50 yards they would probably be around 6 inches at 100 yards — that’s how much and how fast the accuracy drops off.
If I had another life to live I might get interested in testing this myself, but we are talking about years of shooting and it could all end in the knowledge that round balls that don’t spin lose accuracy at longer distances. I already know that, so I’m not interested in testing for it.
How I know
You see, I have tested this already — right here on the blog. I wrote a 5-part series on the Diana 25 smoothbore that showed the accuracy at 10 meters — which was great, and again at 25 yards where it was lousy. That was while shooting diabolo pellets instead of round balls, but in Part 5 of that report I did shoot it with Beeman Perfect Rounds, which are also H&N Rundkugel, and got a large group. So the pellets were more accurate than the round balls, even at close range. That’s how I know what I’m talking about.
How they did it
Those round ball shooters found that the ball had to fit the bore very tight to get the best accuracy. They also found that it did not pay to drive the balls very fast. Beyond that, I really can’t tell you much.
The point is, I think it is an axiom that a round ball can only be accurate close to the gun. At some distance the balls will start to disperse and nothing can keep them from doing that. Balls that are spin-stabilized will be accurate to far greater distances because their spin equalizes any small imperfections in the ball.