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Discussion Starter · #1 ·
I shot some over the chronograph and found my average velocity to be 156fps. This is shooting a 12.5mm (0.50") steel ball weighing about 135gr. with straight cut flat bands purchased from Amazon. They are 23mm wide x 0.65mm thick and I have adjusted them so I have about 7.5" of slack. My draw length is about 27" and the bands are set up shooting OTT on a 3D printed frame. I came to this set up after experimenting with different ammo sizes and band length and I can shoot comfortably without any handslap. Accuracy seems pretty good with me being able to hit a 3" diameter ball on a string about 60% of the time. Question is, is 156fps too slow? I don't have any plans to be shooting competitively, but small game hunting may be in the future if I can attain a level of accuracy to be good enough come this fall.
 

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You could also try some tapered flats so wider at the fork and narrower at the pouch, also for 12.5mm steel some thicker elastic like 0.75 or 0.8mm might be better matched.

Sent from my EML-L09 using Tapatalk
 

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.5 steel at 156 is right around 7 foot pounds, although technically that is "enough" I like to see at least a minimum of 12 foot pounds. Something to consider on the quest for power, if you double your projectile weight, you double your power, but if you double your speed you quadruple your power. So sometimes dropping your shot size and getting some more speed you'll get more power.

I hunt with 7/16" steel and In the summer my speeds are usually 280-290, that's with long draw. but anything over 220 with 7/16 I would say your golden.
 

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Discussion Starter · #5 ·
Is there any "ideal" ammo size for hunting? Or is velocity more important to ensure one delivers sufficient kinetic energy to the target? I do like the 0.50" size due to the feel of the ammo in the pouch and I think it gives me a cleaner release from being able to pinch the ball around the equator more. Are 0.50" glass marbles viable for hunting? They should give me a speed boost without changing the feel in the pouch.

I've got some bandsets from Simpleshot intended for 0.50" ammo. They are quite stout and give me nearly 20fps more with the same 0.50" steel ammo on the same frame. Problem is, they give punishing hand slap. I'm probably going to have to switch to TTF for these bands. I did like how OTT sounded quieter without the bands hitting the frame, hence my using it to try and develop a set up for hunting. Maybe if I pad the frame with the soft side of self-adhesive Velcro it would quiet the bands slap.
 

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With .5 steel and a head shot at that speed I'm sure you'll be fine, but around here game is skittish so at 160 FPS there gonna be long gone before your ammo reaches them. If you plan on hunting with glass I would say your gonna need 5/8 glass and 250 FPS and headshots. Marbles don't have much mass, so it needs to be travelling!!

As for terrible handslap, I think you need to play around with tapers, you don't need a heavy draw with .5 steel. From personal experience I know that .7 elastic cut 1 1/4 x 3/4 with a 10" active will send a 1/2 steel ball at 250 FPS no problem at all with no handslap.

Play around with it!! You'll get it. And it's ALOT of fun trying!!
 

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Discussion Starter · #8 ·
Interesting video. Nice that the shooter has a similar short draw and he obviously is a great shot. Guess I'll be playing around more with bands and ammo and perhaps going to TTF to see if I can't get the speeds up and still avoid the hand slap. Maybe a glove on the frame hand is not a bad idea. I have Mechanix gloves with some plastic scales stitched to the backs of the fingers and hand as an armor or sorts.
 

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Ray Rowden
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I don't think there is one ammo/band combination that is "ideal" for everyone.

You seem to be on the right track with the 12.5mm steel. Your current speed may be a little on the low side, just because headshots aren't guaranteed for most of us. A good thing is that you don't seem to be in a hurry. You can shoot your current setup for a few thousand more shots while figuring out the next step.

You may shoot until you see a band tear near the pouch (the most common spot) and then recut those bands an inch or so shorter than the initial length and retie the pouch. I'm thinking you'll get more performance with a manageable increase in draw weight.

I would keep tapers in mind though. And you may try a set of looped 2040 tubes as well. They are noticeably quieter than flats.

Good luck.
 

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Discussion Starter · #10 ·
Yup. No hurry on my part. I come from a target archery background shooting Olympic recurve for many years. That is all about subtle changes, shoot 1000 arrows, make more tiny changes, shoot some more, repeat ad nauseam. I'm just trying the slingshot thing because it seems very interesting and I like that a lot of my archery training translates over well. It is fun that I can make my own slingshots rather easily with a 3D printer - something not easily done with bows. I'll shoot for 200fps as my next goal for putting together a hunting rig. Perhaps I can design my own frame with a hand protector in front.
 

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Discussion Starter · #11 ·
Little bit of any update. In trying to hit the 200fps mark, I've gone to 10mm steel ammo and went to tapered 0.7mm bands from Pocket Predator. The combination of tapered thicker bands, smaller pouch, and lighter ammo netted me nearly 40fps more and now I am averaging about 194fps. Mathematically, I am shooting with less kinetic energy. The 10mm steel balls average 65gr. and at 194fps, I get 5 ft-lb of energy. The 12.5mm steel balls weighed 135gr. and at 156fps, they generated 7ft-lb of energy. With the heavier Simpleshot bands, the 12.5mm ammo averaged 173fps, giving 9 ft-lb energy. What I do notice is the flatter trajectory of the 10mm ammo at higher speeds, which is nice for accuracy. I found myself hitting the same 3" ball at 10yd more frequently than with the 12.5mm ammo.

For kicks, I shot the 10mm ammo using the Simpleshot bands and hit as high as 239fps which gave 8ft-lb energy. But hand slap was horrible and I have a bruise on my middle finger knuckle as a result! With the Pocket Predator tapered 0.7mm bands, I experimented with length and came to 6-3/4" as my ideal between velocity and avoiding hand slap. Going shorter got me right at 200fps, but I got slapped every time. I'll probably try putting the bands at TTF next to see if I can't stay at the shorter length and still avoid hand slap. Thanks for the help, everyone!
 
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