Shot #1. 3/19/12
Draw length 31″. Draw weight NA. Velocity NA. Glans weight 400 grams. The slingstring was thrown off the limbs. It needs the webbing restraints, just like a regular bowstring. The glans pitched downwards and would have hit the chrono on the bayonet mount if I had not thought to leave it off. I suspected something like that might happen. Bonus point to me.

Shot #2. 3/21/12
Draw length 31″. Other data NA. Rather than use one of our lead glans, the projectile was just an 1 1/2″ length of 1″ round steel bar. It too pitched down, and hit 20′ in front of the machine. However, our webbing restraints worked to keep the slingstring attached to the limbs.

Shot #3. 3/22/12
Draw length 31″. Other data NA. I replaced the leather pouch with one that is much smaller. Projectile was a piece of 3/4″ diameter, 1″ long steel rod, weight 56 grams. This steel cylinder sat snug in the pouch, with the top and bottom string providing a firm grip on the projectile. The shot did not not pitch down coming out of the machine, and held a level course out to the 50 yard backstop. Despite this advance, the weight of the projectile was clearly too light for Firefly’s massive limbs and draw weight. She is essentially working at dry-fire type speeds with this light a payload, (duh!). Velocity did not seem remarkable, however. Something triple the weight would probably be going just as fast. If down-pitching has been eliminated, the chrono can be hooked up again and we can assign velocity numbers to these shots. Then the games can really begin. It is the envelope we seek.

Shots #4, 5 & 6 avearges. 3/23/12
Draw length 31″. Projectile: 56 gram steel slug. Velocity: 242 fps. Energy: 110 fpe. Amazingly bad performance. Might as well be firing frozen peas out of Firefly. No down-pitching though.

Shots #7, 8 & 9 averages. 3/23/12
Draw length 31″. Projectile: 133 gram steel slug. Velocity: 354 fps. Energy: 571 fpe. Although this is still a pretty weak performance, it does indicate an interesting increase in velocity. The only parameter that changed was the more than doubling of the projectile weight. Not at all what one would expect. Clearly there are subtleties at work in how the energy is absorbed from the limbs and slingstring. Flight of the slug was level and on target.

Shot #10 & 11. 3/25/12
Draw length 33″. Projectile: 155 gram steel slug. Velocity on #10: 247 fps. #11: 210 fps. For #11, added a pair of spreaders to keep the top and bottom strings seperated by 1 1/2″. Maybe the extra weight of the spreaders caused the lower velocity. This is all appalingly slow. Spirits low. The machine has a higher tone to it when she fires. Sounds wierd, like she’s not pulling a load.

Shot #12. 3/25/12
Draw lengtth 33″. Projectile: 270 gram steel slug. Velocity: 284 fps. Energy: 746 fpe. Lower tone on firing.

Shot #13. 3/25/12
Draw length 33″. Projectile: 398 gram lead glans. Velocity 290 fps. Energy 1,146 foot pounds. Well zinger do-dandy! That’s more like it. All I did was switch to a much heavier projectile and the velocity went up. How can this be, inquiring kinds want to know? And yet, those are the facts. It flies in face of any physics I know. Clearly there are dynamics at work here I can’t explain. Also the tone of the machine was lower on firing. More like shooting a bolt. I’m thrilled that Firefly has her game back to those older levels from 2 years ago. Bemused as to how.

3 Responses to “Phase 2 glans trials. Continually updated as new shots are made.”


  1. Randi Richert says:

    You do know your baby well. It’s like a parent saying “pick that up before you trip over it” and ten minutes later that’s exactly what happens.

    See my last post on yesterdays thread. Without any downpressure and actually a slight pull upwards, the diving should be eliminated, unless it was caused more by the pocket not opening soon enough or the ends slipping off. The big problem is that my solution would mean a major overhaul. Weren’t you already thinking of something along those lines anyway?


  2. Nick says:

    As a neutral starting point, I made those two green loops that are held by the catch, of equal length. In the previous slingstring from a couple of years ago (see photo from a few postings ago) the top loop was longer than the bottom loop. This gave the pouch a backwards leaning cant. However, I will shoot some more with the current arrangement where the pouch stands up straight. If securing the ends of the string to the limbs doesn’t fix things, we can escalate to a solution from there.

    This excursion into glans-land is a temporary enough venture that I’d be unwilling to do any major overhaul that might deter progess from Firefly’s primary role as a sharps-shooter.

    That being said, don’t be shy! Tell me your plan. I reject enough of my own hair-brained schemes, I can only promise equal treatment under the laws of practical advantage.


  3. Nick says:

    Dear Randi,

    Please disregard the last portion of the above comment. I just now saw your elucidation from the previous thread. Will comment on it after digestion, (ie. putting up my bird boxes).

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