Make cartridges like golf balls?

The facts

Although I am a hunter myself, I have never heard of lead shot being honeycombed like golf balls. And at Kent Cartridge Canada, a major cartridge manufacturer in North America, vice-president of finance Steph Gionet says the company has never made one and that “at [sa] knowledge”, no other manufacturer makes them.

That doesn’t mean it doesn’t exist, but let’s say we’re talking about a very, very rare thing here.

And that’s probably not surprising since, says Yvan Maciel, aerodynamics researcher at Laval University, printing golf ball patterns on the shot “wouldn’t change much.” Let’s see why.

When a ball travels through the air, it must push aside the gases in the atmosphere in its path, gases which will return to their place as soon as the ball passes. Except that it doesn’t happen instantly: even if it only takes a fraction of a second for the gases to reoccupy the space, this creates a low pressure zone behind the ball which will suck it backwards, and slow it down.

Now, when the ball is smooth like early golf balls historically were, this low-pressure zone is relatively large — not far from the diameter of the ball itself — because gases are easily released from said ball. They will only follow its curvature on its front side and will not follow it on its rear side.

However, when the surface is not smooth, explains Mr. Maziel, the roughness will disturb the flow of gases and create turbulence. “It adds energy to the thin layer of air which is in contact with the ball and makes it more resistant to external forces. [qui autrement arracheraient ces gaz de la surface de la balle]“, he said.

Because of this, this layer of air will stay stuck to the ball longer: instead of leaving the surface as soon as they reach the maximum diameter of the ball, the gases will continue to squeeze it. on its back side.

Result: the gases will be less “disturbed” by the passage of the ball, the low pressure zone behind the ball will be smaller, it will slow down the ball less and it will therefore be able to travel further. This is why we print dimples on golf balls.

A few centuries ago, moreover, the first golfers quickly realized that their balls traveled much further when they were worn.

Another aspect of the thing is the rotation that the tee shot will give to the golf ball. This spin occurs backwards, meaning that the top of the ball will rotate in the same direction as the air flow (thus decreasing friction) and the bottom of the ball will rotate against the movement of the air, which will increase friction. And if there is less resistance upwards than downwards, the ball will gain altitude, which will lengthen its flight even more. It’s called the “Magnus effect” in physics, and having relief on the surface of a sphere amplifies it.

Supersonic

Now, if the lead pellets fired from rifles traveled at speeds comparable to that of golf balls, we could extend their range by “dimpled” their surface. This would, however, come with a drawback: as the shots would rotate in all directions, and not only backwards, the Magnus effect would cause them to deviate in all directions.

Which, of course, would prove the presenter Mr. Fleury is talking about right: smooth balls would travel straighter than honeycomb balls.

Except that when it leaves the barrel, the shot spins much, much faster than a golf ball. We are talking here about speeds of around 400 meters per second, or even 500 m/s in certain cases, which is faster than the speed of sound (340 m/s).

“It’s certain that it slows down quickly because they are spheres, it’s not aerodynamic,” says Mr. Maciel. But if it is supersonic, that means that there will be a shock wave which will generate contrails [l’air qui est dérangé derrière un projectile] enormous, and this will continue as long as the ball remains supersonic or at speeds which are not far from Mach 1. So the effect of the cells [qui est justement de réduire ces traînées] would be completely canceled.”

Same thing for the Magnus effect, he continues: “My impression is that the shock wave would dominate all other factors. […] The huge wake behind the sphere can be seen as an effective body [quelque chose qui serait attaché au projectile]and that would cancel out the Magnus effect.”

So ultimately, printing cells on lead balls would make almost no difference to their range or trajectory.

Verdict

Fake. If shot traveled at speeds comparable to that of a golf ball, then yes, smooth pellets would travel straighter than dimpled pellets like golf balls. But the shot comes out of the barrel at supersonic speeds, which creates a shock wave that would completely cancel the effect of the cells.