the diabolo pellet design

[ten.ring]

the diabolo pellet is not a bad or poor design.  i have seen here and on other forums where people are expressing that it is indeed a poor design.

with anything we create and employ into the laws of physics. we are stuck with pluses and minuses. there are many reasons we shoot diabolos out of our airguns, it's not just because they are what is for sale. there are a number of cylindrical pellets out there and they would shoot much better with a much higher twist rate  like 1:6 or so. (the longer the projectile is the more r.p.m it needs to be stable) but that would take some of our limited power and reduce the f.p.s. (the added surface contact in the bore plus the added r.p.m.) have you ever had a dud .22long rifle that went part way down the bore and stoped?  they do not just push out like a diabolo will. if your diabolo is just alittle too tight your f.p.s goes down alot dose it not? the cylindrical pellet will have over penetration in flesh also. the instability of the under spun diabolo helps some to reduce penetration. the skirt on the diabolo allows it to shoot well with less r.p.m.

yes diabolo's have a very high drag (in the air but very very low in the bore. it's a trade-off) but with the relatively low power density of compressed air 900psi-2500psi  v  60,000psi with gun powder.  we can not afford the large bearing surface of the pointed boat tail i use in my 308win. and with a pointed bullet you need a hollowpoint and lots of speed to stop over penetration.

have you tried any of the other options in your airguns.  i have! and nothing even comes close, IF YOUR GOAL IS TO HIT YOUR TEN-RING OVER AND OVER AGAIN AND AGIAN.

round balls could do better in an airgun but the twistrate is TOO fast in any airgun i have had. a round ball only needs about 1 turn in 40 inches. too much r.p.m is not any better than not enough. they have much lower drag BUT have way too much penetration.  low drag in air is low drag in flesh too.

how many of you have found the cylindrical pellets like the ones sharidan sells for the blue sreak  shoot BEST?

i have never seen a group posted for the big bores that was anywhere near what i expect out of my crappy poor design diabolos.  it would benefit the big bores to have diabolos available.

at the velocities an airgun shoots  only round balls a distant second or diabolol's are going to be OVER-ALL consistenly accurate from gun to gun, no doubt some exeptions will accure.  as with all camplicated things we deal with.

mark

[Cal]

On a historic note,  this reference

Subject: Re: Origin of Diabolo-Shaped Pellets?


"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. That function had been poorly served on other airgun projectiles by a series of rather unsatisfactory arrangements: pads of felt attached to the rear of the projectile, spurs or ribs on the projectile, base rings, tails of hair, etc..

hope this helps, best regards, robert"

Dr. Robert Beeman
Airgun Information International
Box 516
Healdsburg, CA 95448 USA

[end quote]

Now on the topic of cylindrical projectiles.  ..

Since the rimfire guys seem to be doing very well with round nose cylindrical ammo at comparable velocities to high energy air guns (30-50fpe)
It would seem that airgunners  could take advantage of the much improved b.c. (3-4X over diabolo ) offered by the design.

Perhaps if a barrel were rifled "lightly", say .001 groove depth.  Bore resistance could be reduced to an "acceptable" level.  OR ..have we seen any reports on the "Smooth Twist" barrels as offered by FX when using "bullets"?

It would seem that a smooth bore with a twisted choke just might  provide some interesting possibilities. 

Still, the final outcome,  success or failure, would hinge on the precision compatibility of rifle bore and ammo.  Just as is the situation with pells.

Samplers any one?   

Cheers

ps I do have troubles with soft lead pells in my high power PCP.  The AR6 blows the skirts out!  Scatter gun at 20 meters!  It's a waste of lead!

[HeadOfPoland]

Nice write up!

[mcc1961]

Very informative.I have just ordered 3 different kinds of Diabolos for a new rifle I am getting.

[mcc1961]

Check out this article I stumbled on.
https://www.pyramydair.com/blog/tag/diabolo-pellets/

[HeadOfPoland]

Check out this article I stumbled on.
https://www.pyramydair.com/blog/tag/diabolo-pellets/

Nice article! Thanks for sharing.

[rsterne]

there are a number of cylindrical pellets out there and they would shoot much better with a much higher twist rate  like 1:6 or so. (the longer the projectile is the more r.p.m it needs to be stable)

In fact the twist rates typical in airguns are plenty fast enough for "bullet" shapes of similar length.... and they would be heavier and have better Ballistics Coefficients than what we shoot currently....  The current trend for benchrest in Europe is barrels with about 1 twist in 14" shooting 41.5 gr. bullets virtually identical to a .22 LR bullet but of 0.224" caliber (.22 cal airguns  are 0.217").... The smallest group I have seen out of Holland is, IIRC, 12 mm at 100 metres (110 yards), shooting outdoors....

Diablo pellets are great at velocities below 1000 fps, and as you say, they have very low bore drag.... However, it isn't the typical 1 in 17-18" twist rate that prevents us from using "bullet" shapes.... In reality, airgun projectiles just have not caught up with the high power of current PCPs, for the most part.... There are exciting times ahead....

However, for 10M Olypic style airgunning, nothing beats a match quality wadcutter Diablo.... Keep it under ~600 fps and within 15 yards and there is virtually nothing more accurate.... 

Bob

[Cal]

Check out this article I stumbled on.
https://www.pyramydair.com/blog/tag/diabolo-pellets/

Nice article! Thanks for sharing.

The Author was much maligned in this recent thread:

http://www.gatewaytoairguns.org/GTA/index.php/topic,38865.0.html

[WarBirdII]

Enjoyed the article.

[mcc1961]

Check out this pic I saved of a plane breaking the sound barrier.

[charlesdias]

Very interesting arguments. Indeed these trade offs in airgun pellets physics not worthy. And there is a point we need to consider ... always ... that the gun doesn´t necessarily "likes" the pellet physics says would be the best for it.

[ten.ring]

for some one who does not care how much air is used for each shot the limitations of p.c.p. pressures have much much more to offer that to those who have to pump their air by hand.

there is more than one idea out here in the pellet gun world about what a airgun is expected to do.  for me if i want sub m.o.a. at 100yds and 160f.p.e. i get my cz 452 put some cci stingers in it.  1656f.p.s.  32gr about 3 1/2x on the b.c. .103   but thats just me.

i like the low power. the diabolo slows down fast  i can shoot at a bird on a wire and the pellet is going to come down in my state. i can shoot in places i can't safely shoot the powder guns.
so quiet  even without the tko, i have a lic for the one on my cz  but it's not leagal to hunt with it on.

i can see the intrest in looking for the max range and power of the pcp, engineering challanges can be quite captivating.

for the pellet gun  or  the diabolo-gun that is under 1000f.p.s.  the diabolo can't be out done.
a cylindrical pellet at 1300f.p.s.  would be a bullet  exept for what pushes it down the tube.  i got bullet pushers.
mark

[dryanw]

I'd like to try a bullet shaped pellet in .177 to see how it would do but the only one I know of is the JSB Jumbo which weigh like 16 grains or something crazy like that....

[ten.ring]

there are quite a few cylindrcal pellets out there do some web searches,,  i know if we ask our fellow forum members to help we can list them right here.  so i'm asking !!  most of the ones i've seen are heavy  but they would have to be  or they would be very short or hollow.

bob how fast are the bench guy's shootin the 41.5's? are they round or pointed, boat tail?  ??  tell us more please.  this thread is about pellets and why they are what they are. and what is the proper use of the differant types.  i am hoping to clear up myths and ledgans with knowledge.  if someone buys a 2 door sportscar to haul fire wood it's not gm's fault it does a poor job at that task.

for a guy tryng to get rid of a bunch of foxy nutters  who have seen too many of their family die,  a longer range tko'd p.c.p. would be of GREAT value.  but the shooter would need to know what pellets to use  more importantly  why one pellet is better than the next.

mark

[ean]

Mark I agree with your basic precept totally.  I also agree with many of your correlated thoughts.  Finally, I never disagree with Dr. Beeman--within the scope of his work.

Having said that, I am working on the machining for a boatail .22 pellet that will use a discarded plastic airseal/rifling engagement.  My hopes are to develop the rotation without increasing the barrel drag, and at the same time increase the pellets BC to .06 or above.  So far, my tests seem to indicate a minimum weight of something a bit over 18 grains.  Pretty much maxed out for anything but a PCP, but I am stubborn...I keep tinkering.    My initial goal was to find a pellet for my D460.

I agree with your desire to know your pellet landed in the state of origin, but the pellet is not going that much further, no matter the BC--my goal is to simply flatten the trajectory a bit and carry the energy a bit further downrange. 

Remember that we have available materials and manufacturing methods that were out of reach even 15 years ago.

[Motorhead]

Sure am liking the JSB 10.3's in .177
Real accurate in around 900 fps and still amazingly accurate pushed near 1100 fps !

https://www.pyramydair.com/product/jsb-diabolo-exact-heavy-177-cal-10-34-grains-domed-500ct?p=388

Not your typical diabolo shape

[ean]

Scott, did you change your avatar pic slightly?  It is still cool, but I think the old one told more of a story. 

[Motorhead]

Scott, did you change your avatar pic slightly?  It is still cool, but I think the old one told more of a story. 

I did ... original was this

[ten.ring]

pushing the envelope of technology is what got us into space and why we get better milage AND more power out of our car engines.  and why i love my new pelletguns more than my old ones.  i do not argue that a .06 bc would be of no value only that the diabolo is the best for it's intended purpose. when someone expects a product to do well outside of its desgned purpose they are wrong to blame the designer for the poor performance.

the diabolo is not the only missunderstood projectile.  the m16 firing the 223 orinally had a 1:16 twist rate which was intentional to slightly understablize the 55gr fmj bt at 3300f.p.s.  (to try and make up for the 1/3 bullet wheight of the 308) the slower r.p.m. than optimum causing it to yaw when it was suddenly slowed down by entering flesh and there by making a larger wound chanel than the same bullet fired at the same f.p.s.  but with a 1:12 that was ideal if you were after long range accuracy. the m16 had a lot of lore about how it was designed to enter you in the shoulder and leave out your knee.  the general puplic thuoght it was some sort of magical bullet.

yes i know there are lots of new materials avail today  i am a machine designer  by trade,,   and lots of new applications everyday  thanks to people working to push the technology to the next level.

your challenge  will be two fold it will be difficult to get the sabott to separate without disturbing the light little pellet. and whether or not the 1:16 twist at your f.p.s. will give you the r.p.m. needed for long range stabillity, after all the cylindrical pellets purpose is longer shots.  IT HAS BEEN A VERY LONG TIME SINCE I WAS INVOLVED WITH PROJECTILE DESIGN  AND I AM GOING ON MEMORY..  I HAVE NOT CALCULATED THE GYROSCOPIC STABILLITIES HERE  BUT YOU CAN FIND THE EQUATIONS TO DO IT YOURSELF. one problem you are going to run into is the calcs will not take into account the stablizing afect of the skirt of a diabolo because it is not a solid object like a bullet so the sg value will not be right because it's vallue is assuming a silid bullet shape, plus we do not know the alloy.  the cylindrical pellets will be much easier.  http://kwk.us/twist.html  this is just one i had handy there are better ones out there. i find the twist rate this program gives to be on the very minnimal end of stability. for a convetional modern bullet. except for short range shooting and then they are fine.

mark 

[Cal]

I enjoy pellets and air guns for the intended purpose.  They are so back garden and neighborhood friendly!  There is no shortage of pell calibers, weights, and configurations.  But there is a extreme shortage of ammo that offers  ballistic performance that is a match to the 30-50 foot pound guns.   There is no reason Not to include that range.  The market might be small,  but it should be healthy with all the excitement about 100 yard accuracy and .25 and .30 caliber guns.

90% of shooters don't need a "bigger wound channel",  they just want to see energy down range.  Weight and BC will do that.

I have no desire to go to .30 or .50 caliber just so I can purchase cast ammo that performs as desired.  .22 is fine!