Home
Blog
Credentials
Articles
Links
Article originally appeared in Airgun Revue #3
by Tom Gaylord
The airgunner of
yesteryear was a happier person than his modern counterpart.
If he wanted to see how accurate his gun was, he shot at something.
If he hit it, he looked for a smaller target to shoot until the
parameters of accuracy were firmly established. If the gun had
to be held right or left, high or low, or some combination of
these, he was willing to do it because that was the way the gun
shot. Period!
It worked the same way for velocity. If the projectile made it
to the target and did whatever was expected of it, velocity was
adequate. Punching holes in paper is easier than downing large
game animals, and our simple countryman with his primitive airgun
was smart enough to know that. He lived at a time we now call
B.C. - "Before Chronographs."
Unfortunately, for those of us on the cusp of the third millennium,
writers of earlier times were also hamstrung by the lack of instrumentation.
Their descriptions of velocity, power and accuracy sounded like
political speeches, filled with subjective words like "substantial,"
remarkable," and "amazing." All of which gave
rise to a body of half-truths and downright prevarications regarding
the power of ancient big bore airguns.
Today, an airgun maker has to build his big bore pieces to compete
against the airguns of history, which reportedly threw huge lead
balls at 900 f.p.s. with sufficient accuracy to kill a man 100
yards distant. It would be nice to fire these oldies once again
so the claims could be verified, but of course they are both
too valuable and too embrittled by age to permit that. So, they
repose at permanent rest, shielded by their value while the myths
about them continue to grow.
New info about old guns
Except for one thing - airgun maker Gary
Barnes has conducted tests showing that round lead balls
deform along rigid lines until the ball is completely fragmented
by the force of impact. Here's the big news: this phenomenon
happens irrespective of caliber! His claim is that all lead balls
deform in more or less the same fashion when they impact a rigid
steel plate at a given velocity. A .350-caliber ball impacting
a steel plate at 350 f.p.s. will look the same as a .535-caliber
ball going the same speed, except for the difference in size.
Thus is born the science of "splatology," or the study
of lead "splats" to determine the impact velocity of
the ball that created them.
Barnes noticed this relationship very early in the testing of
his first big bore guns. The phenomenon was so intriguing to
him that he made up "splat boards" containing a spectrum
of lead balls that had impacted at different velocities. These
he mounted in series, ranging from lowest velocity to highest.
The velocities were obtained from an Oehler model 35 chronograph
placed in front of the splash plate. He then carved the velocity
for each ball into the wood next to the recovered splat. All
his splats were produced by a one-inch steel splash plate that
stands perpendicular to the flight of the ball, so it is identical
to the plates mentioned in the early airgun documentation.
It doesn't matter when
it was shot - a splat tells the same story forever!
It is important to keep in mind the fact that
the splats reveal only the velocity upon impact. If the actual
muzzle velocity is desired, additional calculation is required.
That depends on how far the muzzle was from the impact point.
Fortunately, this distance is sometimes given in literature.
It's possible to calculate velocity for tests conducted a century
ago, providing the splat is accurately represented (usually by
a drawing, but in this century photos were also used), and the
distance to the plate is given.
The "splash
plate," as it is called, must be rigid for the results to
be consistent. If not, some of the ball's energy will be used
to move the plate, which results in a splat that looks like it's
going slower.
We know the ancients were aware of this phenomenon because it
is mentioned in their notes. In W.H.B. Smith's book, The Standard
Encyclopedia of Gas, Air and Spring Guns of the World, the
author mentions that European makers were still testing the power
of their modern pellet rifles in 1956 by firing them against
steel splash plates.
Today, we put our trust in modern chronographs that instantly
display the numbers we convert to love or hate our guns. But
only a few people have any clue as to what those numbers mean.
For example, is 600 f.p.s. slow or fast? If you're looking for
the most powerful pellet gun in the world, it's probably slow.
If your pellet just hit the paddle of a field target at that
speed, it's probably just right.
How to calculate velocity
without a chronograph
Older English writings state that big bore airgun
velocities were gauged by flattening the ball against a steel
plate at a specified distance. In the book Air Guns and Air
Pistols by L. Wesley, there's a photograph of flattened balls
shot from an air cane, representing the progressive lowering
of velocity as the pressure dropped. It's obvious to anyone who
sees the photo that lower velocity results in a ball that is
less flattened.
With this technique, it's possible to examine the older writings
about big bore airguns and determine the impact velocity from
drawings of recovered balls. Since the steel or iron plate test
was a common one when these guns were new, there are several
drawings of flattened balls that accompany the guns. Caliber
doesn't matter, remember, since all balls exhibit the same characteristics
when they impact a metal plate at the same speed. Here's an abbreviated
version of Barnes' observations:
At or below 250
f.p.s., the ball will be smashed perfectly flat on the impact
side, with the opposite side still round. It will look like a
perfect hemisphere, with little of the ball spreading out from
the edges of the hemisphere.
At 275 f.p.s., the edge of the ball starts fanning out from the central hemisphere. Barnes calls this "feathering."
Above 300 f.p.s., the hemisphere that was intact starts to thin out. It is no longer a true hemisphere.
At 350 f.p.s., the remainder of the ball begins to look like it is "melting" toward the sides, which are now starting to show signs of separating into both large and small "petals".
At 400 f.p.s., the ball is nearly flat and separated into distinct petals. Little remains of the original hemisphere.
At 450-480 f.p.s., the balls are completely flat, and the petals are tearing deeper toward the center of the ball.
At 550 f.p.s., the petals are well-formed and very deeply separated. After this point, they start to break off.
At 600
f.p.s., the ball has lost two-thirds of its petals. Now, the
center of the ball starts to look like the whole ball did at
450 f.p.s.
At 609-610 f.p.s., a strange thing happens. The center of the ball recoils off the splash plate, and the petals that remain attached to the center recoil back towards the steel plate.
At 650 f.p.s., only the center of the ball remains. Sometimes, it looks like a smaller whole ball, but often there are angular sides and irregular shapes, where major petals were joined. The surface that struck the steel plate is now pointed in the center.
At 675 f.p.s., the center of the ball is smaller. It is starting to disintegrate into flakes.
Above 700 f.p.s., the center is destroyed; only flakes remain. You can taste vaporized metal in the vicinity of the splash plate.
Test your new splatology
skills!
Click here to try
your hand at guessing the velocity of various splats. The featured
splats went through the chronograph at recorded speeds. See if
you can guess their velocity by comparing them to the splat boards!
This new science was christened "splatology" by my
wife, Edith, and we have declared Barnes to be the Father of
Splatology. What Gary has done for us is deserving of a round
of applause, for it levels the playing field across the span
of time. No longer do contemporary makers have to live in the
shadow of earlier times, when the laws of physics were still
just rough drafts. Now, we know how fast and powerful those old-timers
really were. All it takes is the evidence of just one splat.
Have you hugged your splatologist today?
Thanks to Gary Barnes for providing the splats with recorded velocities for this article.