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Diabolo Projectiles in Un-rifled Barrels: Do They Work Well?
Posted: Sun Sep 18, 2011 8:05 pm
by danielrowell
I've been curious about this for a while now. Has anybody ever tried launching a diabolo-type projectile from a cannon with an un-rifled barrel and, if so, did it fly without tumbling?
Diabolo projectiles have a pinched waist and a higher weight bias in the nose. The high air resistance on the back of the projectile is supposed to prevent it from tumbling. Pellet guns commonly shoot diabolo pellets since their rifling isn't as effective in stabilizing the projectile as it is in conventional rifles, and the diabolo style is supposed to be reasonably effective in smoothbore guns.
Posted: Sun Sep 18, 2011 8:19 pm
by saefroch
In theory it should stabilize if the skirt is fitted to the barrel ID. However, finned designs or those with a different tail material tend to be a better bet for a smoothbore.
Posted: Sun Sep 18, 2011 8:23 pm
by danielrowell
Oh...Now I feel kinda dumb for asking.
Posted: Sun Sep 18, 2011 8:30 pm
by Moonbogg
Sureshot sells them (plastic spudgun pellets with metal noses) and yes they work very good.
Posted: Sun Sep 18, 2011 9:47 pm
by Gippeto
Only made the one to prove a point...it punched a round hole though.
My thinking is that the diablo slug IS slightly better for smooth bore airguns than the foster slug. Less drag in the barrel, and the skirt obdurates easier to seal the bore.
Greater angle exposed to airflow should also increase stabilization forces...minimizing "wobble" and working well over a broader velocity range.
BUT....having made both types...the foster slug is a heck of a lot simpler to make an effective mold for.
Posted: Mon Sep 19, 2011 12:21 am
by jackssmirkingrevenge
Dr. Beeman wrote:The diabolo shape of modern airgun pellets was developed empirically early in the 20th century. The key reason was the simple matter of greatly reducing friction in guns which had so much lower power than firearms. The diabolo pellet has the minimally required two stabilization points, fore and aft, but no friction between them.
Concomitant with this was the concentration of weight in the head which is a trick used by the developers of many other projectiles: sabots, "mini-balls"., lawn darts, badminton shuttlecocks, etc. to stabilize the flight of the projectile.
And, as a very large bonus, perhaps realized at time, was having a thin skirt which would be expanded, even by the relatively weak blast of gas from an airgun, to nicely seal the projectile into bores of such widely divergent sizes as those of German and English airguns of the supposedly same caliber.