# The effect of band/pouch weight relative to projectile weight on speed/power.



## Henry the Hermit (Jun 2, 2010)

It is obvious that the heavier the bands and pouch the less energy will be transferred to the projectile. I noticed this a couple of days ago when comparing two slingshots with 107 bands cut to the same length but with different pouches. Since it seems no one until now has bothered to quantify the effect, I decided to run some tests. For this first set of tests, I chose Alliance Sterling #107 rubber. Three naturals of nearly the same size and shape were set up with 7.5 inch bands (frame to pouch tie). The beech fork, from Germany, has a Rayshot Super Pouch. The unknown wood fork from North Carolina has a Jim Harris pouch and the other is Nance from Panama and uses my Shoot Anything shoe leather pouch.

The active portion of the rubber weighs 150 grains / 9.8 grams. It is generally accepted that the bands must accelerate half their own weight, so band weight will be 75 grains / 4.9 grams. By adding projectile, pouch, and half total band weight, we get the total weight that the bands must accelerate. Divide the projectile weight by the total weight and we obtain a projected efficiency of the bandset/pouch/projectile combination.

Below is a chart showing the first tests. This is very preliminary and I will do a lot more testing when I have better weather/light conditions than today.









Yes, those are actual, Chrony generated speeds, but bear in mind, I always have warm weather, except when it's hot. and I stretch the bands as far as I can. All three band sets are new, and only have a dozen or so shots on them so far. I expect a lighter draw and more speed as they get broken in. The three sets performed almost exactly as predicted in the chart, with the lightest pouch having the highest average speed, and the heaviest, the lowest.

More tests, pictures, and video to follow.

Edit: I neglected to mention that the balls are .44 cal lead weighiing an average of 121 grains.


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## ash (Apr 23, 2013)

Good work.

The lighter the ammo, the more pronounced the effect of pouch weight.


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## Rayshot (Feb 1, 2010)

I know somebody will notice this so I figured it may be worthwhile to point it out. In the description it has my SuperPouch at 24 grains, but in the chart it is 16.8. Since my SuperPouches in the 5/8 and 3/4 are all close to .9 to 1.1 or 1.2 grams (appx 17 grains) I noticed the difference. Thus according to what likely the pouch's weight would be, I assuming the chart is the correct weight for the SuperPouch at 16.8 grains.

Hopefully, this helps and not make a mess.

Thanks for this Henry


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## Henry the Hermit (Jun 2, 2010)

Thanks, Ray. I had a Senior moment and have removed the incorrect weight. The weight in the chart is what the pouch weighs.

Ash, you are correct and that will be clearly demonstrated when I start testing lighter ammo.


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## Flatband (Dec 18, 2009)

Nice work Henry! Good stuff!


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## Henry the Hermit (Jun 2, 2010)

I caught a break in the weather and made a quick video. This is with 7.5 inch bands using a Rayshot Super Pouch and .44 lead. Please excuse the focus problems. It's still cloudy and the light wasn't real good.


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## poekoelan (Jan 1, 2013)

Really awesome. I never would have thought that 107s were capable of that. I bet your quick release adds something to the mix. Thanks for sharing.


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## Greavous (Sep 29, 2013)

Interesting data. I was experimenting with my setup a while back and made some major changes to my pouch size and it did seem to shoot more snappy. I use Kroo leather and weighed my last pouch on a kitchen scale and it was less than a gram (zero) so Ill have to go dig up my gun powder scale and get a grain weight. I went from a 5/8" wide x 2 5/8 long pouch down to 9/16" x 1-7/8" which is real small. My thinking was like this... you arent supposed to pinch the pouch in front of the ammo but rather squeeze the sides of the ammo (how I do it anyway) so why have all that extra leather between the ball and the holes that tie the bands? My current pouch is just enough to manage the ammo and no more. I have to go find that scale now.


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## Henry the Hermit (Jun 2, 2010)

I apologize for the lack of further tests. I'm preparing for a trip to Texas and hurt my shoulder last week, so further tests will have to wait until I return.


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