To wit:

His velocity measures of CO2 and non-CO2 suggest that balls do indeed slow down LESS.... than pellets over a distance.

The velocity data in each case was averaged for muzzle, and subtracted by the average of velocity....at 10 meters.

For the first non-CO2 example:

(To save you the simple math.)

Average muzzle velocity of 3 pellet shots = 546.7666

Average 10 M velocity of pellets = 516.0666

Difference in velocity = 30.7 FPS

Average muzzle velocity of 3 ball shots = 506.1666

Average 10 M velocity of balls = 475.9

Difference in velocity = 30.26 FPS

For the second CO2 example:

Average muzzle velocity of 3 pellet shots = 563.6333

Average 10 M velocity of pellets = 540.6666

Difference in velocity = 22.966

Average muzzle velocity of 3 ball shots = 515.8666

Average 10 M velocity of balls = 504.5333

Difference in velocity = 11.333 FPS

ineedpals CO2 discharges were highly controlled compared to the pump gun measures, and BOTH suggest that ball shapes do travel more *efficiently(*less drag) in the air than pellets.

This is exactly the data format I had hoped for from the shooters. Speeds & groups organized well. Thankyou ineedpal!. -LarryS

## ineedpal's data indicates what I had suspected....

### Careful with the interpretation...

The math works out ok, and the numbers seem pretty close to what we'd expect, but the interpretation I think might be off a bit. (and "indicate what I expected isn't good science )

The numbers certainly show that the balls slow down less. Unortunately linking this observation directly to the "efficiency" of the shape is misleading. There are a couple ways to approach the analysis of this test, and what I'm presenting is a very rough no-calculus method.

(Switching to SI units - sorry, I've assumed 14.3gr vs 15.56)

If we look at the initial

Energy at 10m gives us 11.47 for both projectiles. This obviously means that the ball has lost a larger percentage of it's initial energy, which doesn't bode well for drag down the road.

Relating energy lost back to force (over 10m - this is a bit dodgy since the force isn't constant, but it's good enough) we end up with a drag on each shot of .14 vs .15 N. The sphere is experiencing *more* drag than the pellet. It is being helped long somewhat by it's higher mass, but it is still losing out.

And the kicker. A big reason LarryS' back-of-the-envelope has trouble is that the pellets start at different speeds. The ball is draggier even though it is travelling quite a bit slower, and this is going to hurt. Drag on a projectile increases relative to the square of the velocity. Working out the drag coefficients, using the muzzle speed (another kludge), we end up with .35 vs .44 - a 25% advantage to the pellet. These numbers line up pretty closely with published data...

There are lots of solid reasons to play with ball ammo, but maybe aerodynamics isn't one of them? A little digging on the web turns up lots of past work on the subject.

Interesting line of questioning though!

Matthias

The numbers certainly show that the balls slow down less. Unortunately linking this observation directly to the "efficiency" of the shape is misleading. There are a couple ways to approach the analysis of this test, and what I'm presenting is a very rough no-calculus method.

(Switching to SI units - sorry, I've assumed 14.3gr vs 15.56)

If we look at the initial

*energy*of the pellet vs ball, we see 12.87 vs 12.97 Joules. The ball is heavier, and aiguns seem to eek out a little extra with extra mass to move. Otherwise, everything is as we expact, and the initial energy values are close.Energy at 10m gives us 11.47 for both projectiles. This obviously means that the ball has lost a larger percentage of it's initial energy, which doesn't bode well for drag down the road.

Relating energy lost back to force (over 10m - this is a bit dodgy since the force isn't constant, but it's good enough) we end up with a drag on each shot of .14 vs .15 N. The sphere is experiencing *more* drag than the pellet. It is being helped long somewhat by it's higher mass, but it is still losing out.

And the kicker. A big reason LarryS' back-of-the-envelope has trouble is that the pellets start at different speeds. The ball is draggier even though it is travelling quite a bit slower, and this is going to hurt. Drag on a projectile increases relative to the square of the velocity. Working out the drag coefficients, using the muzzle speed (another kludge), we end up with .35 vs .44 - a 25% advantage to the pellet. These numbers line up pretty closely with published data...

There are lots of solid reasons to play with ball ammo, but maybe aerodynamics isn't one of them? A little digging on the web turns up lots of past work on the subject.

Interesting line of questioning though!

Matthias

If continued investigation results in more confirmation that the rate of velocity loss of a skiirted pellet is greater than the ball...... we will need some way to explain those facts.

I have long since contended that a skirt "Parachute" will dramatically slow down anything in motion thru the air. My motorcylce was installed with a contoured windshield.... it lost enormous velocity when coasting and accelerating. So did my old racing boat stern in the water as a medium until I raised it with speed rails to cut the cavitation. Same way with the racing props on it. Lastly a badmitten(sp?) again illustrates the effects of skirt shape although it is further modified by venting.

It seemed a logical answer to the facts given me. -LarryS

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Fwiw, the co2/2289 set of numbers are completely bizarre when compared to one another. I'd be interested to hear possible explanations for the co2 ball moving only 8fps faster initially losing a third the velocity of it's 2289 cousin. More testing, and careful setup in order.

Aerodynamics is a funny subject. Our pellets are moving fast enough to have a definite "wake" behind them, where the flow seperates. Anything you tuck into that area of disturbed air is more or less invisible in terms of drag. A fast moving sphere

*already*has a "parachute" of air tumbling around behind it. The skirt of a diabolo protrudes into the free stream a bit (otherwise there would be little point) but the added drag isn't as much as you'd think, and you get some benefit from a sharp trailing edge (just like you speedboat).

Your badminton example is a good one. If you can get a hold of a couple of shuttlecocks, try throwing one as hard as you can. Do the same with one with the venting taped over. Now imagine throwing a sphere that weighs the same and has the same frontal area (calibre). A birdie's mass is only about 5 grams - maybe compare to a ping pong ball at 2.7g? (with only a 1/4 the frontal area)

Hopefully someone can contribute some "heavies" for your tables. I think it might help!

Matthias

A shuttlecock and pellet are quite different in design. The head of the shuttlecock is a lot smaller than the tail. The air catches this wide spread circular tail and stabilizes the flight quickly. With a waisted pellet, the circular tail has the same diameter as the head. The tail does not stick out passed the side of the head.

Maybe someone can find a good pic of the air currents on a pellet that is shot at say 800fps. It would be interesting to see how much air the skirt catches. Maybe there is something on the net already. As was illustrated with the above testing(1st set) the ball doesn't retain energy any better than the pellet for the first 10 metres.

Ball (15.56gr) looses 0.0316FPE

Pellet (14.3gr) looses 0.299FPE

Todd

It was a drag(pun) and I gave up searching.

The physics of that particular shape are not easily described because it envolves much more than frontal and waist analysis. The tail is complex initself because of sharp angle and the concave chamber within it.

As was just mentioned.... we need identicle weights with identicle initial velocities to even BEGIN resolving or describing why it is happening. Without this identity and without further test data the jury is still out as to whether it in fact is even occuring. I just happen to be biased that it is true.......until tests contradict me.

ineedpal..... gonna send you a mess of graphites and copper clads to play with for your observations on accuracy and grouping. You did a great job assembling the data into a comfortable structure. And it only LOOKS like it was easy to do the measures. I know differently, on what it took to gather that much information.... it was VERY HARD & TAXING!.

TNX.! -LarryS