Posts Tagged ‘Chairgun’

Testing trajectories in the past

by Tom Gaylord, a.k.a. B.B. Pelletier

Before we begin, here’s an update on my good friend Earl “Mac” McDonald, who’s contributed so much to this blog and has enriched my life and the lives of many who participate here. He’s at home, being cared for around the clock by a home-care nursing staff. That will soon transition into home-based hospice care, as his condition will not improve. He knew I came to see him, and we spent a lot of time together in the two weeks I was there. If he could, he would thank everyone who’s sent him good wishes and prayers.

Today’s topic came in about a week ago, and I put it in my bank of reports to write while I’m on the road. Although today is Monday, I’m still traveling home from seeing Mac. The distance was so great that I broke it into a 3-day trip, and was planning to stop by the American Pickers store in Nashville. I got there before they opened, and hundreds of people were already waiting in line to see it. So, I decided to just continue driving home.

The question is: How did shooters of old test their trajectories? How did they know where to aim for the longer shots?

I suppose the answer breaks down in several ways. Buffalo hunters, for instance, shot just one load in their rifles so that one load was all they had to learn. The land over which they shot was mostly flat and dusty so they could see the strike of the bullets when they hit the ground. Over time, they learned where to set their sights to hit animals at different ranges, and they used the feedback they saw downrange to refine their understanding of the ballistics of their rifles.

Then, there’s the scientific approach, which is based on mathematics. Calculations can be made to predict the flight of the bullet with good precision, then they’re verified and refined by empirical testing on the range. One of the best-documented instances of this is the development of the cartridge that became the .45 Government, or what we know today as the .45-70. That cartridge started out as a .50-caliber round; but through range studies and exhaustive testing they discovered that the .45-caliber bullet had better ballistics. If you’re interested in this sort of thing, there’s a very thorough report of the entire cartridge development in M.D. (Bud) Waite and B.D. Ernst’s book, The Trapdoor Springfield.

Though the timeframe for this development was the late 1860s and early 1870s, scientists knew a lot about how projectiles flew ballistically — and they had good mathematical tables to help them with their research. Ballistics was already an established field of study when this cartridge was developed.

But what about the amateurs? What did they do? Some were able to use the same tables as the scientists, and they used their own ranges to confirm and tweak the results of the calculations. But they didn’t have Chairgun back in the 19th century, so whatever did they do?

What’s Chairgun?
Chairgun, and now Chairgun Pro, is an airgun and rimfire ballistics software that helps you plot the trajectory of a pellet before you shoot. It has become a great favorite of airgunners who use it to set their scopes for different ranges with different pellets. Field target competitors find it especially useful because they need to know the exact place in the trajectory their pellets will be at all ranges. Those pellets must pass through small holes in the front of the steel targets they shoot at in order to hit the triggers in the back of the targets and knock them down. If their pellet partially hits the face of the target as it passes through the hole, it can lock the target in the upright position and it won’t fall — robbing the shooter of a point. But the Chairgun software and lots of testing helps the shooter refine his pellet plot so he gets it in the right place every time.

And the good news is that now they have a version that works on Mac computers, too, so I’ll finally be able to use it!

But 150 years ago, there were far fewer personal computers — so what did those people do to determine the actual trajectories of their bullets? Well, to paraphrase the movie, The Graduate, I have two words for you — tissue paper. They lined up tissue paper screens between the muzzle and the target, and shot through them to “watch” the drop of the bullet over distance.

Now, before some wiseacre scientist in the crowd pulls the Heisenberg principle card on me, I’m aware that passing through even one sheet of tissue paper does have an effect on the ballistic flight of the bullet, however slight. I’m also aware that a bullet isn’t a subatomic particle, but I wanted to get that idea off the table so we could discuss the thing that “they” really did in order to measure the flight of bullets.

When Dr. Mann did the 37 years of work that eventually lead to his book The Bullet’s Flight, from Powder to Target, he used tissue paper screens at regular intervals between the rifle and target. He wasn’t looking for the trajectory as much as he wanted to know the attitude of the bullet at various distances from the muzzle. In his day, it was suspected that bullets left the bore unstabilized and then stabilized as they went downrange. So, he was looking for the pattern of elongated holes on the screens that would indicate yawing bullets.

How did they align the screens?
If you have ever given this approach any thought, you must have wondered how the screens were aligned. For example, if all the screens are supposed to be the same height above the ground from the muzzle to the target — how is that done? You don’t just set them on the ground and hope they line up; because no matter how flat the ground may be, there are still variations of several inches at various points along the bullet’s path. But these people wanted those tissue paper screens to be aligned within the tightest variation possible.

Today, we’d use a laser and place the screens so each one aligned with the laser’s dot; but just as computers were in short supply back then, so were lasers. So how did they do it?

They used a surveyor’s transit to align each screen. Because of the nature of what they were doing, they had to start placing screens at the target and work backwards to the gun because each screen obscured everything that was beyond it. With a laser, you work the same way. The only difference is that one person can lay out a range like this with a laser, while a transit takes at least two people. If you’ve never tried it, don’t make light of it, because you cannot imagine the difficulty of aligning all those screens. And, if the wind is blowing, you might as well give up because the screens will never settle down.

Did it work?
Some of you know this works because you’ve tried it yourselves. Yes, it does work. The tissue paper needs to be stretched tight on the screens so it doesn’t tear. That isn’t as important for firearm bullets as for airgun pellets, but the paper does need to be fairly flat for every bullet or pellet. And airgunners usually don’t need to place screens out beyond 50 yards or so, while in the past firearms shooters often placed them out several hundred yards.

For an airgun, an interval of 5 yards is useful. For firearms going out to long distances, a 25-yard spacing might work better, though closer to the gun so that spacing might be reduced to 10 yards.

A modern anecdote
In the early 1990s, several government physicists wrote papers that criticised the story of Billy Dixon, the buffalo hunter who shot an indian off his horse at 1,538 yards during the second battle of Adobe Walls, Texas. It took him 11 shots to find the range. The physicists said it wasn’t possible for a .50-caliber bullet weighing over 600 grains and leaving the muzzle at 1,250 f.p.s. to even go that far, let alone to hit a target way out there. So, several shooters convened at Fort Huachuca, Arizona, where the U.S. Army had a millimeter wave radar to track their bullets in flight.

What they learned astounded them. A bullet from Dixon’s rifle could go over 2,500 yards, and the Army’s .45 Government bullet went past 3,000 yards. Even though they were subsonic much of the way, these bullets were proven to have very great range. This experiment could not have been done with tissue paper, since the barrels had to be elevated 30 degrees to the horizon.

Summary
I hope this answers the question our reader asked about how trajectories were verified in the past.

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