Roundball accuracy in smoothbores

by B.B. Pelletier

I’m now back home. My surgery was successful, and I’m on the mend and on the road to complete health. While I’m tired, I feel better and have more energy than when I was in the hospital. I’ll be able to address some blog questions but not all. I’d sure appreciate any help our regular blog readers could give in answering some of the questions.

A fair question to ask is why roundballs are not as accurate in smoothbores as they are in rifles. While it may seem counterintuitive to most people that a spherical object could need stability in flight, in fact it does. When you spin a spherical object, you’re promoting stability by averaging the instability in the object. Here’s what I mean by that. When you spin a sphere, you set up an arbitrary north-south pole. And, whether or not the object is fully stabilized by this spin, it’s more stable than if it had no spin at all. That’s because you’re making the heavier and lighter parts of the sphere rotate around the spin axis.

Now, to be sure, there’ll be one spin axis that every sphere likes better than any other, but the probability of you finding that axis when loading a sphere into a rifle is quite small. The Earth isn’t stable. It precesses the axis around an arc of 22.1 to 24.5 degrees every 26,000 years.

Something probably closer to home, at least for those in the U.S., would me a major league baseball pitcher who throws a leather-covered spheroid in a certain way to make it do specific things. For example, if he rotates it fast around the axis of the seams, he creates a low-pressure area on one side of the baseball. That causes the baseball to move in a certain direction that we’ve come to call a curve ball. But, this same trick can be used on other axes to cancel drag; and when that happens, the pitcher throws a fast ball.

But this isn’t a lesson on the Earth or baseballs. We’re talking about round spherical objects shot from guns. What can you expect from them? Well, one thing we’ve recently learned from the unusual world of airsoft is how to throw a fast ball. I don’t mean a baseball-type fast ball, I mean a perfectly smooth spherical shape thrown as a fast ball. We simply stop the top of the ball from moving as it goes down the barrel, which makes the bottom of the ball spin upwards. The ball then goes straight much farther and doesn’t curve to the left or right. This is what hop-up does. But, we don’t have hop-up BB guns except for a few that are now being produce with the BAXS-type hop-up. While it may be interesting to pursue that technology in relation to BB accuracy, that’s not what I want to do in today’s report. I want to talk about what people have been doing all along to get an accurate smoothbore BB gun.


“The world’s most accurate BB gun” – the Daisy Avanti 499 Champion.

Back before the Daisy 499 came out, there were two other models that were used for the International BB Gun Championships. Both were Daisys, and one was the model 99 and the other was the model 299. While I’ve never owned a 299, I have owned a 99 and can tell you that it’s about as accurate as the recent Chinese-made Daisy No. 25 I tested, i.e., it could group 10 shots inside an inch at 15 feet. But, that falls far short of what we know is possible, so what’s made the difference?

Coaches used to run through their shot tubes and test each of them in their guns and return them to Daisy for other shot tubes when they wouldn’t hold a certain level of accuracy. This got to be so prevalent that Daisy caught on and figured out what they were doing was looking for the shot tubes that were the best fit to the BB. By “best fit,” I mean two things. They were the tightest and they were the most uniform. So, Daisy undertook the design of a radical new BB gun — the one that was to become famous at the “the world’s most accurate BB gun.”

The 499 is unique in that it’s one of the few BB guns that have been made in recent years as a single-shot. It’s also a muzzleloader. When a BB is dropped down the muzzle, it can take 3-5 seconds to roll all the way down the bore to the magnetic seat at the bottom. So, we know the bore is tight. The muzzle velocity is in the 250 fps range, which tells us that high velocity is not a requirement for close-range accuracy. But, the fit of the BB to the bore of the gun certainly is.

I’m telling you this because I’ve recently discovered that the new RWS BBs that are so smooth on the outside are also slightly larger than the Avanti Precision Ground Shot made for the 499. So, I intend to conduct a side-by-side accuracy test between them and the Daisy shot. I’ll test them in a 499 and also in the new No. 25 pump gun that we now know is so accurate. This should be a very interesting and thought-provoking test.

But, that’s not really what this report is about, is it? The title says “roundball accuracy in smoothbores.” I’ve told you this before, but here’s a reminder that in the mid-19th century, there was a club in Ohio that attempted to see what type of accuracy they could get from roundball shooters in smoothbore guns. I don’t have a lot of data on their success, but I believe we’re talking about a couple of inches at 50 yards. Of course, the tightness of the patch would be a factor, the positioning and size of the sprue (the small flat spot left by the cut-off plate used to cast the ball) would matter as well as the homogeneity of the ball itself. That is, there should be no air voids or deposits of crystalized metal inside the lead ball.

For many years, I’ve given some thought to testing a round lead ball shooter. However, if a more homogeneous steel ball is available, I don’t want to waste my time chasing homemade artifacts over which I have little control except for sorting. So, it may be that we have a super-accurate BB that can now answer the question, “Can a roundball be accurate in a smoothbore barrel?” Or, perhaps, the better question is, “How accurate can a roundball be in a smoothbore?”