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OMG Zwillie...that cannot have been easy to do !!

I'd love to hear more about this. Technique of insertion and performance.

I've only tried two types of cocktail tubes (full length). One was Green DubDub with a natural latex inner...which is still going strong and another with 50/80s with 20/40s inside. These were great but unfortunately the 50/80 snapped after not very many shots so I haven't bothered again
 

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"So, what a coincidence that our band measurements are so close."

Great minds think alike!

"What would be the best way to tie off the short loop?"

I use black waxed string that I buy from my local leather shop. It's roughly the same diameter as the cotton kite string I used to buy, but much stronger.

Now for the good news.

I did it!!!

attachicon.gif
chrony-300-01.jpg

And here are the bands I used. Length of one side 6.5 inches. The loop is just long enough to fit well on the Dankung. BTW, with the amount of shooting I'm doing, the Dankung is just too uncomfortable, so all future tests will be with Mr. Stubby. I've found no difference in performance but a huge difference in comfort.

attachicon.gif
looped-single-300fps.jpg

Now for some BBs.
What size tubes are you using. I would like to use your design. (Copying is the highest form of complimenting!!! LOL)
 

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I use a partial butterfly draw when shooting that comes out to 62in or 157cm. I also shoot 3/8" steel (and 5/8" marbles that weigh close to the same) and I'm looking for the right setup.

I've been using 1745 tubes but they are a little too slow for my liking. I want a FAST setup, something that will turn that 3/8" steel into a penetrating projectile. But I'm a little lost because it looks like Henry's tests were done with a draw that is almost half the length of mine. Should I just scale it up?
 

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I use a partial butterfly draw when shooting that comes out to 62in or 157cm. I also shoot 3/8" steel (and 5/8" marbles that weigh close to the same) and I'm looking for the right setup.

I've been using 1745 tubes but they are a little too slow for my liking. I want a FAST setup, something that will turn that 3/8" steel into a penetrating projectile. But I'm a little lost because it looks like Henry's tests were done with a draw that is almost half the length of mine. Should I just scale it up?
You should get Henry's take on this, but to me "scaling it up" would be to use the same stretch factor (ratio of stretched total length to unstretched total length, with same ratio of 1-tube to 2-tube section unstretched lengths). This will give you the same draw force as Henry, but the increased draw length from butterfly will increase the projectile energy by about the ratio of draw lengths, and the projectile velocity by about the square root of that number.
 

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Discussion Starter · #311 ·
What size tubes are you using. I would like to use your design. (Copying is the highest form of complimenting!!! LOL)

"So, what a coincidence that our band measurements are so close."

Great minds think alike!

"What would be the best way to tie off the short loop?"

I use black waxed string that I buy from my local leather shop. It's roughly the same diameter as the cotton kite string I used to buy, but much stronger.

Now for the good news.

I did it!!!

attachicon.gif
chrony-300-01.jpg

And here are the bands I used. Length of one side 6.5 inches. The loop is just long enough to fit well on the Dankung. BTW, with the amount of shooting I'm doing, the Dankung is just too uncomfortable, so all future tests will be with Mr. Stubby. I've found no difference in performance but a huge difference in comfort.

attachicon.gif
looped-single-300fps.jpg

Now for some BBs.
All these tests were made with 2040 or 1842 tubes, available from dankung.com or TrulyTexas.com Pre-made tube sets are available from some of our Vendors.
 

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Discussion Starter · #312 ·
I use a partial butterfly draw when shooting that comes out to 62in or 157cm. I also shoot 3/8" steel (and 5/8" marbles that weigh close to the same) and I'm looking for the right setup.

I've been using 1745 tubes but they are a little too slow for my liking. I want a FAST setup, something that will turn that 3/8" steel into a penetrating projectile. But I'm a little lost because it looks like Henry's tests were done with a draw that is almost half the length of mine. Should I just scale it up?
For 3/8 steel, 2040 will work best. Stretch the tubes as far as you can and cut them accordingly. I stretch mine to ~600%.
 

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OK, I know that some of you guys are bored with all the discussion of lb/ft, because velocity is where the glamour is. So here are the results so far, of velocity measurements, from which the energy figures were derived. Note that with 39.7 grain .30 cal lead, pseudo-tapered outperforms looped. The looped configuration doesn't show a clear advantage until projectile weight reaches 125 grains. (.429 lead) I'm guessing that the crossover point is about 100 grains, but don't have any 100 grain ammo.

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avg-velocities.png
hello sir, looks as if 2040 out performs 1842. so you say you wanna make these tubes scream at 600% correct? so what length must tubes be so that 30" is 600% , and how would i figure this?
 
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