# Flashed steel balls - faster?



## JoergS (Dec 17, 2009)

It is a known fact that the dimpled surface of a golf ball increases its speed and stretches the flight curve.

The famous "Kugel Winnie", who supplies all kinds of steel ball ammo to us German slingshot afficionados, suggested that this might work for slingshot ammo as well.

So he sent me a sample box with a few dozen 20 and 10 mm flashed steel balls, and - for comparison - the same sizes in polished and hardened condition. Great gift! Thanks, Winnie.









Basically the flashed balls are taken out of the machinery before the grinding, polishing and hardening stage.

I will perform some tests, shot from a sling-x-bow, as I have to shoot from a longer distance and pretty much have to hit bulls eye every time to not endanger my trusted chrony.

Will be interesting!

Jörg


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## BCLuxor (Aug 24, 2010)

sounds interesting .... I assume however that at the relatively low sub 600fps the effect won't be that great however I'd love to be proven wrong! surely the same effect could be achieved by soaking the polished steel in a vinegar bath to remove the smooth surface...


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## bullseyeben! (Apr 24, 2011)

Interesting, I v have some marbles that's surface closely resembles that of a golf ball, i would have thought the extra surface area would have the opposite effect? i am looking forward to your conclusion.. Ben


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## justplainduke (May 31, 2011)

From good ol' wikipedia: 
A ball moving through air experiences two major aerodynamic forces, lift and drag. Dimpled balls fly farther than non-dimpled balls due to the combination of two effects:

First, the dimples on the surface of a golf ball cause the boundary layer on the upstream side of the ball to transition from laminar to turbulent. The turbulent boundary layer is able to remain attached to the surface of the ball much longer than a laminar boundary and so creates a narrower, low pressure, wake and hence less pressure drag. The reduction in pressure drag causes the ball to travel further.


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## justplainduke (May 31, 2011)

The second is backspin, which we do not have to concern ourselves so much with.


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## bullseyeben! (Apr 24, 2011)

Go Wikipedia hey, makes sense, I did think the fast spin of the ball some how combined with the dimples helped stabilize the flight, sort of like rifling in a barrel.. good to know. But launched from a bow will it obtain enough spin? I'm excited!


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## slingshot_sniper (Feb 20, 2011)

Very interesting topic









I have some 9.5mm ones Bill Hay's sent me,I don't have a chrony and can't tell the diff but if it turns out they can be faster....maybe sandblasting existing polished ones would have the same affect


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## Gwilym (Dec 9, 2010)

There was an episode of myth busters were they tested dimples on a car. The myth was that a dirty car is more fuel efficient than a clean one cos of the dimpling effect (it wasnt). But then they covered the car in modelling clay and cut dimples out the clay to make it like a golf ball and the result was it used less fuel. Heres a link 
http://www.megavideo.com/?d=VKSNEPJO
I think that you need the perfect dimples to work not just a rough surface so I dont think these balls will work however I dont think there will be much difference and they should be cheaper cos there is less processing required. I may well be wrong though and am looking forward to the results.


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## whipcrackdeadbunny (May 22, 2010)

co-efficient ballistics.


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## jskeen (Feb 7, 2011)

Interesting indeed. I'm not sure that simply having steel shot with a rough surface will give the same decrease in drag that the regularly spaced uniform dimples on a golf ball do, but I'd sure like to be proved wrong. I recall that Frogman said a while back that he intentionally wets his steel shot down and lets them sit out to rust, because he likes the rougher surface to make it easier to grip the ball through the pouch.

That flashed surface looks a lot like the finish I get on my 50 cal cast lead black powder bullets after I run them overnight in a tumbler full of sand. They come out uniformly dull with a rough matte finish that looks very similar. More importantly, to me anyway, the peening action of the shot rattling against each other and the sand almost completely removes the casting sprue and leaves them nice and round.


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## Dayhiker (Mar 13, 2010)

OFF TOPIC, sorry. . . but, Joerg, I sent you a pm. Did you get it?


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## Bill Hays (Aug 9, 2010)

This should be an interesting experiment.
One thing though... if you put a twist on the pouch, turning it even a little like 1/16 - 1/4 of a turn... I've noticed rough surfaces tend to bite the air and can get some pretty wicked curveball action.
So when ever I shoot precision shots I always use the smoothest ball bearings possible... because my normal pouch hold is slightly off of straight for the side shooting method.... and is turned slightly more than a 1/4 for the forks up hold.

With the forks up hold using a PFS and shooting small marbles (which are obviously not balanced) I can sometimes get a 3 foot curve in 90 feet... and using rusty steel balls up to 18" in about 90'.... but if shooting smooth steel ammo, most of the time no curve at distance out to 210'.

So what this shows is the rough surface definitely bites into the wind... whether it acts like golf ball dimples is another thing...


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## Tex-Shooter (Dec 17, 2009)

Well now I think that it is very easy to slice a golf ball. I don't know if that means anything! -- Tex


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## shooter452 (Nov 6, 2010)

Tex-Shooter said:


> Well now I think that it is very easy to slice a golf ball. I don't know if that means anything! -- Tex


I used to play golf with a guy that would duck and curl after my drives (busting my chops) thinking the banana curve would bring it full circle. It was that pronounced. Although not provable by my game a golf ball started straight will stay straight and vice versa. Great point.


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## dgui (Jan 12, 2010)

My Balls pick up lots of speed after I soak them in vinegar for a few minutes. Didn't I bring this up several months ago?

Putting steel balls in vinegar for about 15 minutes causes them to become rough even pitted and they grip in the pouch better and since they are no longer slick they are easier to pick up. 

Steel Balls Plus Vinegar either white or cider equals Faster Balls.


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## Nico (Sep 10, 2010)

dgui said:


> My Balls pick up lots of speed after I soak them in vinegar for a few minutes. Didn't I bring this up several months ago?
> 
> Putting steel balls in vinegar for about 15 minutes causes them to become rough even pitted and they grip in the pouch better and since they are no longer slick they are easier to pick up.
> 
> Steel Balls Plus Vinegar either white or cider equals Faster Balls.


I remember reading that thread dgui, twas intriguing and pretty cool..


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## jskeen (Feb 7, 2011)

Bill Hays said:


> This should be an interesting experiment.
> One thing though... if you put a twist on the pouch, turning it even a little like 1/16 - 1/4 of a turn... I've noticed rough surfaces tend to bite the air and can get some pretty wicked curveball action.
> So when ever I shoot precision shots I always use the smoothest ball bearings possible... because my normal pouch hold is slightly off of straight for the side shooting method.... and is turned slightly more than a 1/4 for the forks up hold.
> 
> ...


Bill;

I'd really be curious to see if you get this effect using dgui's etched steel ammo. Also, is this effect dependent on the size of the projectile? Is it more apparent with smaller shot, as the mass to surface area ratio is lower as the diameter decreases? How bout I send you some vinegar?


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## bj000 (Jul 21, 2011)

bullseyeben! said:


> Interesting, I v have some marbles that's surface closely resembles that of a golf ball, i would have thought the extra surface area would have the opposite effect? i am looking forward to your conclusion.. Ben


i have these golfball looking marbles too.. they tend to curve in flight. i do not know if they are any faster or anything.. i just noticed a curve.


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## GameKeeper (Jul 24, 2011)

Well what can I say







the "holes" in ball should be bigger, that structure don't remind me a golf ball. But it should not slip when shooting. Thats why some peoples like to eatch their ammo, and rusty steel can be better than shiny ones









Well its aerodynamics. You cant win with this


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## Guest (Aug 17, 2011)

i wonder if this thread will be updated :s


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## danielh (Jul 28, 2011)

whats the most aerodynamic shape out there, im sure it comes from nature, raindrop maybe?


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## Guest (Aug 17, 2011)

the drop that comes out of the water as a raindrop splashes down? ever see that?


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## danielh (Jul 28, 2011)

ya but im just thinking the air molds the shape so maybe raindrop shaped ammo, lol


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## Jacktrevally (Feb 14, 2011)

You can try raindrop/teardrop shape. I was making them before and don't need a mould. However, a ball spins when travelling in air so does the tear drop shape, this is important.

I believe the least surface area for the biggest volume will be faster shape, and that is a sphere.


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## danielh (Jul 28, 2011)

id love to see a write up and maybe test results from some engineers on pushing the limits of slingshot ammo. The slingshot it's self is a fine machine, maybe more performance could be had from ammo, i dunno, im more of a purist but this stuff is interesting, just like flight shooting in archery so much goes into arrow design and bow design.


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## GameKeeper (Jul 24, 2011)

Jacktrevally said:


> You can try raindrop/teardrop shape. I was making them before and don't need a mould. However, a ball spins when travelling in air so does the tear drop shape, this is important.
> 
> I believe the least surface area for the biggest volume will be faster shape, and that is a sphere.


You are right. Water can turn its own shape, it tryes to make a ball but cant. Any other material that cant change shape just WONT WORK







If You dont belive me just try this out.

You want to watch this. Ant thats why it must to be a GOLF BALL sufrace. Flashed balls just dont be so good. Well as I said its aerodynamics, cant win with it


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## strikewzen (Jun 18, 2010)

because i am an airsoft fanatic here's one of the best projectile design in the past

it was able to travel much further without any spin and least affected by sidewind

but i think someone should come up with a pouch that is able to shoot this... maybe like a barrel with front opening perhaps something like this:


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## GameKeeper (Jul 24, 2011)

-Harder to make than ball
-Harder to shoot than ball?
-Harder to get than ball?
-Harder to buy (more expensive?) than ball?

BUT if it would be more accurate than ball as You said I would consider to buy it! Its greate info!


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## strikewzen (Jun 18, 2010)

yes it's true, i can't even find one of the originals as it's been recalled by japanese government after someone modified the gun that goes with it to fire 0.22 cal (one of the original ASG was sighted in hong kong for 3000~5000 usd) ok.. and immediately someone bought it

however, if it were made into a lead cast mold we'll be able to make as many as we want, and it's definitely harder to shoot no doubt

if anyone wants more info the projectile is called: the blade bullet
designed to be fired with Asahi M700 and M40


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## Jacktrevally (Feb 14, 2011)

You are right about the tear drop. A drop from free fall of a liquid varies with density and viscosity provided that the constant like pressure, temp... etc are the same.

You can do the experiment with 2 chronys but I doubt you will get visible results as the constants are small in air and speed involved with a slingshot might not be critcal.

If I had to do it, I will used the same in a more viscous fluid and use that as a model. The relative speed and relative densities of the fluid can be model as if the projectile is moving in air. By calc you can prove either a the flashed ball is faster in air. It look obvious to me since I've done mathematical modelling in fluids but a pain to understand for a first timer.

Let move on to scientific experiment I've read. A projectile can be streamline but not necessarily travels faster. It cnan have the same weight and volume but the aspect ratio is critical. A projectile can be flat and short yet having a resonable drag coefficient compared to a longer slender and aerodynamic projectile.

I've learnt from fluids mechanics that for a ball in turbulance (therefore flashed) the drag force is calculated differently than a smooth ball which doesn't have turbulence which behaves like a car. Very complex for me even I've done it, Cd they call it and B a dimensionless constant for turbulent situation.

Time for a beer I woukd say and lets enjoy shooting.


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## NaturalFork (Jan 21, 2010)

But I like my balls nice and shiny.


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## Hit and run (May 14, 2011)

If you take into consideration the speeds the average slingshooter shoots at and the distances then drag doesn't really come into play for 10mm ammo or larger.

Little example:
- ammo 10 mm steel (no dimples)
- distance to target 100 meters
- launch speed 65 m/s or 213 fps

When this steel ball reaches the target it lost 0.6 m/s or 1.8 fps in speed due to drag. (With dimples it will have about 80% of the drag assuming the same Cd as a golf-ball, which is rather optimistic imo.) Put the target at 10 meter and you can divide the speed lost by 10.
A 20 mm steel ball will loose half that and a 1/4" BB looses almost twice that.
The 20mm one will reach the target 0.004 seconds earlier than the 10 mm one.

Now have a look at some chrony tests here on the forum. Those easily vary 5 to 10 fps between shots.

Even if you think this matters, it wont if you miss the target because the thing doesn't fly straight.

(The reason it makes quite a difference for golf-balls is because they have a lower average density)

edit:
Thought I'd add the speed lost for a dimple-free 15mm glass marble: 1.5 m/s or 4.5 fps. (over 100m @ 65m/s)


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## GameKeeper (Jul 24, 2011)

Man but we talk about increasing speed from start, and increasing accuracy (You actually can increase speed of projectile just changing its shape!). I really think it can help even when the projectile is dense.


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## Jacktrevally (Feb 14, 2011)

It can certainly help but the effect with a slingshot would be negligible as the speed is low compared to the mass ratio of the projectile you can launch with a hand held slingshot!


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