Ok since no one replies to my topic, I did my own testings recently, and heres the results, though not sure who's gonna read this
Till this day, I've never fired broadhead darts, only bamboo skewers and concrete nails, mostly for target shooting. So for my new upcoming hunting blowgun build, I wanted to experiment with some things
I made an experimental 20mm(apx 7.87 cal) 4 foot long BG , sole purpose of determining the max. caliber for my lung capacity, and a experimental equally big, huge, literal 'dart'
it's SK-5 steel, 2mm thick, besh wedge grind geometry. not so much pics in making, since it only took an hour...
after heat treat.. quenched and tempered to chocolate brown, then filed down to final dimension
cut a green fresh oak sapling. it was extremely soft to work with. I completely shaped it and quick-dried it up with oil lamp
after mounting broadhead on shaft
intentionally made it tapered, to make it front-heavy. With kitchen scale, dart weights around 8~9gram, which is quite heavy for a blowgun dart.
So how did it turn out, anyway? From this test I could've made 3 conclusions
1. yes, I know. you can't see from this blurry pic, but steel broadhead dart DOES scratch the bore. Again, I know, this is far too obvious, don't even worth an experiment, but I just wanted to test out and see it myself. In this experiment, with my copper tubing BG, sometimes even the broadhead dug into the barrel and stuck, I had to ram it out with a stick. After few of this happening, I inspected my tubing. What I've found was a deep gouging marks, and highly visible linear scratch lines.
I have no idea how cold steel blowguns hold up even if they're made out of aluminium. maybe this scratching problem doesn't really count as long as the darts are light enough so that they do not dig into the barrel as they accelerate. still they would scratch the bore, which is quite inevitable without a protective sabot
but to completely avoid scratching, one may use bone/antler/non-ferrous metal broadheads as alternatives.
2. 20mm bore is too big to blow. With this caliber, the drag of the dart cone was so huge, as it flies thru, I could even see it wiggle side to side, almost like a koi fish.
and with the lighter darts, such as bamboo skewer, I could not exert enough power through as I could with smaller caliber blowguns. guess it has something to do with not only the total volume of the inner bore, but also with peak pressure. Or maybe the dart had lost all its energy, again, due to huge drag on its wide tail cone.
One could solve this problem if discarding sabot is used, but then, I have no idea of how that could even be possible with such a light projectile as blowgun dart is.
3. Still, in close range, the dart was powerful enough to penetrate a book, more than 100 pages. (sorry, I forgot to take pics) But what about it? Worthless if it can only slowly thrust up to 10 feet at max. As said, drag seems to be too high. Presumably, .625 cal is best compromise for my lung volume, power and aerodynamics.
so for me, .625 cal, 4 feet long blowgun would be ideal choice. hmm still, I wonder would longer BG will result in better efficiency, though. Anyways, I'll come back with more results as I progress.
btw if any one of administrator in this forum is viewing this, i do not mind this post being moved to 'darts board'. but you know, everything is relevant with blowgun, and I'm doing all this for sole purpose of hunting
