Photos by Helen Lewis
copyright 2004 Precision Shooting Magazine
Two neighbor boys, Joe and Will, and I were hunting red squirrels (Chickarees) on a warm summer day. In Pennsylvania , there was no season on these elusive targets, and we hunted them strictly for bait for our weasel sets. I may as well explain that the Pennsylvania Game Commission back then paid a one dollar bounty for each complete weasel hide sent to them. The hides had no monetary value in the summer and weren't returned unless requested.
Since we weren't having much luck with the red squirrels, an empty pipe tobacco can was set against a stump some 60 yards away, and each shooter would fire three shots and then check the can for hits. I drew the short straw and began firing from a sitting position. When I fired the second shot, Will claimed he had seen the bullet on its way to the target. Naturally, we disagreed with him and told him it was impossible to see a bullet in flight. He told me to shoot some more and ask Joe to sit beside him and watch.
Four shots later both claimed they saw a flash of the bullet. It dawned on me that they might just be pulling my leg to get me to shoot all my rimfire ammo. To beat them at their own game, I told Joe to shoot while I watched with Will. To my surprise. I did see a flash when Joe fired the first shot. We were puzzled about seeing a bullet in flight and concluded that my ammo was defective. I can't recall what brand or type of ammo I used, but since 22 Shorts were three for a penny at the local store, I have a strong feeling Shorts were being fired.
At that time, we knew practically nothing about ballistics. There was little published data, and we assumed if the bullet could be seen, it had to be traveling at about half speed. The truth leans more to the bright sunlight and the angle to the sun that we were shooting. Since then, I have seen flashes of bullets and even shot charges when watching shooters on my line fire at claybirds.
I do recall an argument in the country store between my brother Dan and several old time hunters. They had a rather heated debate on how the speed of a bullet was determined. I can't remember exactly what was said, but Dan claimed it was done with an electronic timing method. I'll leave the argument now since it would be pure guesswork what he meant. But in all fairness, bullet speed was calculated by an instrument that clocked the time of a bullet between two points. The time was then translated into feet per second.
In 1961, I purchased a Herter's chronograph which times a bullet's flight between two precisely placed screens–usually ten feet apart.. When the bullet hit the first screen it started a crystal clock and stopped the clock when it hit the second screen. The time of flight was shown by a series of numbered lights, and the time figure was checked against an interpolation table to change it to feet per second. My Avtron K-233 was a super precise instrument that used the same method. Instead of woven wire screens, the K-233 used a painted screen, but the principle was the same. The first 
screen for high velocity cartridges was normally place ten feet ahead of the muzzle. The two screens were exactly ten feet apart. This gave an instrumental velocity at 15 feet----ten feet to the first screen and half the distance between the screens
Let's step back to the 1700s when Benjamin Robins invented the pendulum system for measuring velocity. The pendulum is essentially a block of wood of known weight suspended by a chain of known weight. At the bottom of the block a length of tape was fastened. When a bullet of known weight was fired into the block, the block moved backwards. This distance was measured by means of the tape on the block. With the weight of the bullet and block known, as well as the weight of the chain and distance of the rearward travel of the block, velocity of the bullet was readily calculated. The pendulum velocity measuring system has long been replaced by the modern chronograph, but some form of the old pendulum system is still used to measure recoil.
It's probably true that the old pendulum system made velocity “readily available”, but I have a sneaky idea it took more than a knowledge of Long Division to calculate it. Not every cartridge designer or gun maker was able to “readily” calculate it. They claim, and I firmly believe it, that necessity is the mother of invention. When something complicated has to be done, there is usually a less complex way of doing it. This was the case with bullet velocity, and here's one method, unscientific as it may be, that cartridge designers came up with an estimated velocity. Under controlled and safe conditions, a bullet weight of known velocity was fired into a metal plate. The new cartridge, with the same bullet weight, was also fired into the same plate. By measuring the depth of penetration of the two bullets, it would be obvious which bullet was faster. If the factory cartridge had a known velocity of 2300 fps, and the test cartridge had more penetration, the cartridge designer would know the test bullet had a greater velocity and this led to some wild velocity claims.
One of the wildest velocity claims that a friend told me was about two handloaders who built a 12 caliber varmint rifle. The case was a necked down 22-Savage Hi-Power, and the bullets were made by machining them from steel rods. Their claim of 5500 fps with a maximum powder charge has to be a pure guess since back in the early 1950s, home chronographs were not available. But there is another problem. Barrel manufacturers claim that making a barrel below 17 caliber is exceedingly difficult and expensive. It wouldn't be financially feasible to tool up for just one barrel. Also, what about the rate of twist. At that speed, it would have to be as slow as possible. Pure steel bullets passing through a bore at more than a mile a second would ruin a barrel in short order. With a bullet weight probably below 15-grains, accuracy would be out the window. My friend stated the builders claimed the bullet's inability to expand allowed it to pass through the rib cages of foxes and coyotes without making an instant kill. Whether this actually happened is questionable. I think it was all fiction and some writer's imagination working overtime.
I bought a Herter's chronograph in 1961. Actually, I think it was accurate, but hooking up the woven wire screens with sloppy alligator clips was a hit and miss affair. A screen is good for just one shot, and every failure cost two screens. There was no positive way that I recall of knowing when the clips were making full contact.
The Herter's chronograph was just a timing device that gave the time the bullet spent between the two screens spaced ten feet apart. Numbered lights lit when a bullet passed through the screens, and by adding the rows of light number, the total sum was checked against a table that showed how fast the bullet was traveling in feet per second.
The Avtron K-233 operated on the same principle, but used plastic screens with a continuous line painted on the screen. When a bullet broke the line on the first screen, the K-233 began to count and stopped when the bullet cut the line on the second screen. A digital readout gave the time the bullet spent between the two screens and using the Avtron's interpolation table translated the time figure into feet per second. I rarely had a failure with the screen hookup, but at 12 cents per screen, it cost 24 cents for each shot or $1.20 for a 5-shot test.
I got a lot of use out of it for a few years, but when the manufacturer phased out the K-233, screens were no longer available. Sometime in the early 1970s, I purchased the Oehler Model 11/61 Chronograph/skyscreen system. It, too, showed the measured time which had to be checked against a table provided to get the instrumental velocity. However, the skyscreen boxes were superior to wire or plastic screens.
In the Model 11 chronograph, time is measured by counting the ticks of a very accurate electronic clock. The clock is a crystal controlled oscillator delivering 400,000 pulses per second. These pulses are counted by an 
electronic counter controlled by the Skyscreens. The electronic eyes (silicon phototransistors) of the Skyscreens continually look at a segment of the sky through the small slot in top of the Skyscreen box. As the bullet enters the field of view, the amount of light seen by the eye decreases by 2 percent for roughly 50 millionth of a second. The eyes convert this small change in incident light level to an electrical signal/ which ultimately controls the chronograph. Simply stated, when a bullet passes over the first skyscreen box, its shadow starts the clock ticking and stops the clock when it passes over the second box.
The Oehler Model 11 got a real workout for several years, and I even set it up in the shop using a bullet trap for 22 ammo using artificial light provided by two long filament “Slim Jim” bulbs (showcase lamp bulbs) mounted about 18-inches above each skyscreen box. In one major rimfire test which took about six weeks, Helen and I fired more than 1000 rounds over the skyscreens.
When Oehler brought out their 35P chronograph sometime in the 1980s, I purchased a 35P in 1988. The 35 P Oehler is a compact unit that consists of a chronograph that incorporates a printer. Instead of having just stop and start Skyscreens, the 35 P has a third screen (middle) called a “Proof” screen which will be explained later.
The 35P use a 9-volt alkaline battery. Naturally, there is no set life time for a battery, but Oehler says battery life should be around 25 hours including 1000 print lines. A weak or cheap battery may not operate the 35P efficiently. I keep a new spare, and change batteries at the first sign of battery failure..
The normal setup for the 35P is to place the first skyscreen 10 feet from the muzzle. With an 8 foot screen spacing, this gives an instrumental velocity at 12 feet. By adding the velocity loss of the first 12 feet to the instrumental velocity gives the muzzle velocity. To do this, check a factory ballistic chart and find the velocity loss in the first 100 yards for your bullet and your approximate velocity. Divide this figure by 25 to find the velocity loss at 12 feet or 4 yards.
The 35 P shows a good bit of data on the tape. It shows the proof reading, shot number and primary reading. Under these figures is a Summary Table showing the high shot, low shot, extreme spread, average velocity and standard deviation.
Skyscreens are at the mercy of the existing light conditions at the time of testing. Although skyscreens work quite well under most light conditions, but under certain conditions there will be errors. They might not be frequent occurrences, but they do happen, and the proof screen gives you a warning if a measurement error is likely to have occurred on any shot.
Theoretically, the proof channel should be the same velocity as the primary channel. Theoretically, and rifles shot one-hole groups at 100 yards. I guess that's enough of theory. In actual shooting, the proof channel velocity will vary slightly from the primary velocity. The differences between the two velocities on each shot are caused by small measurement errors. The sizes of the differences are comparable to the sizes of typical errors in your velocity measurements. The primary channel is typically twice as accurate as the proof channel because it uses twice the spacing between screens.
Screen spacing is of utmost importance. The stop screen is exactly 4 feet from the start screen and the proof screen is exactly dead center between the two screens or 2 feet . Oehler suggests a 4 foot spacing between the start and stop screens, but longer spacings will give a more accurate reading. No matter what the distance is between the skyscreens, the measurements must be exact with the proof skyscreen at the precise midway point.
I won't get involved with Oehler's Personal Ballistic Laboratory (PBL) since it is an article in itself. I will simply say its ability to show chamber pressure in literally any rifle and also give the downrange velocity and ballistic coefficient ( when the Acoustic Target is used) puts it in a class by itself. It should be a must of the serious cartridge designer or bullet maker.
The compact Competitive Edge Dynamic (CED) chronograph is small enough 
to slip into a coat pocket. Its skyscreen setup is on a hinged rail that fits on a camera tripod. The screen spacing is 2- feet. I place the first screen exactly 9 feet from the muzzle. This gives me an instrumental reading at 10 feet/
This compact unit offers s the highest velocity, lowest velocity, extreme spread, average velocity and standard deviation. The CED chronograph will accept over 220 shots (data entries) and up to 20 “strings.” To review shot entries which have been stored into strings, press and hold the “RE” (review) button for three seconds. All data can be stored into a back-up memory until it is either erased or printed out. It also can be downloaded into a computer.
One unique feature is the Speaker Key (SP). Press the speaker key when you wish to hear your data entries in addition to seeing them. It does not function when in “review” of data entries. I think the retail price of the CED is under $200.00. For more information, FAX (610) 366-9680.
It's been a few years since I worked with a Shooting Chrony, made by Shooting Chrony, Inc. 1-800-385-3161. The Shooting Chrony really qualifies as a compact unit. One model contains the entire system in a metal box that unfolds and can be fitted to a camera tri pod. Custom rifle builder, Jim Peightal of Ernest , PA claims for his work the Shooting Chrony can't be beat. I might mention that the Master Chrony is used with the Ballistic Printer. From my own experience and Peightal's claims, the Shooting Chrony is a reliable instrument. Chrony says, “If it doesn't unfold, it's not a Chrony.”
A chronograph is an essential piece of ballistic equipment for every handloader. There's little that can be done in cartridge reloading or load development if the velocity is not known. Some may argue against my view, but, after 42 years of chronographing, I'm willing to bet my last two cents that I'm right
