Other alternative ways to achieve spin stabilization

[CreationInk]

Hi peeps,

A newbie here. Over the past few months I've been researching pcp air rifles with the goal to design and make 1 (for) myself. During this process, it got me thinking of alternative methods to achieve spin stabilization of the pellet/slug other then rifling the barrel or making a polygonal barrel with a twist.

I've been wondering, is it possible to spin the pellet through airflow alone? By "rifling" the airflow behind the pellet, which in turn would spin the pellet as it is propelled forward by the air. The reduce friction and increase the effect of the "rifled airflow", maybe a very small gap between the barrel and pellet is needed.

Any insight and/or related comments are greatly appreciated.
Also happy holidays everyone, hope you have a good one.

 

[AlanMcD]

Honestly, I don't see any practical way to do it. Even if you could get the air to spin down the barrel, the projectile would have to be modified in shape to be able to impart the spin force on to it - like with fins. And then there is the matter of getting it to spin fast enough - while the rifling of the barrel does not look like much in terms of spin to the naked eye, we have to remember the impact this has on a projectile moving very fast: even a slow twist barrel has a 900 fps pellet spinning in excess of 18,000 rpm as it leaves the barrel. That's a lot of spin to impart directly from just an air blast . . .

 

[Peashooter]

I dont think something like that would work.
You could Nozzle so the released air would be released in a way it would spin, but i think as soon as the pellet / ball are just a little away from the nozzle that spin effect would diminish as the pellet / ball get further and further down the barrel.
Now as you say if you could shape the projectile to be the nozzle that would spin air as it go thru the gap between pellet and barrel that would not loose affect, but i still think such a pellet would be hard to mold, and the loss of air would be undecidable.
Also as mentioned above i think it will be very hard to this way get the spin up to a number of RPM that is useable, here the grip of lands and groves are instant and the same from the very first mm of the shot to the last mm before the pellet leave the barrel.

Speaking of alternative, i just saw someone are planning to launch satellites with steam powered rockets, or at least steam powered 1 and 2 stages of the rocket.
Not that i am promoting steam rifles, just going alternative my brain remembered that.

FX old ST barrels is probably the most easy way, with just rifling the very last 2 inches of the barrel, work fine too, i have always been impressed with the performance of my FX Cyclone.

 

[CreationInk]

Honestly, I don't see any practical way to do it. Even if you could get the air to spin down the barrel, the projectile would have to be modified in shape to be able to impart the spin force on to it - like with fins. And then there is the matter of getting it to spin fast enough - while the rifling of the barrel does not look like much in terms of spin to the naked eye, we have to remember the impact this has on a projectile moving very fast: even a slow twist barrel has a 900 fps pellet spinning in excess of 18,000 rpm as it leaves the barrel. That's a lot of spin to impart directly from just an air blast . . .

Hi Alan, thnx for sharing your thoughts. I was thinking more along the lines of using the "no-slip" condition to impart the rotational force onto the pellet/slug, so a longer smooth surface (slug) is more ideal. Similar to how a tesla turbine works (bladeless turbine), with smooth discs, evenly (very small gap) spaced from each other. There of course allot of differences, but maybe it's still worth trying. Not having to clean the barrel or breathing in lead dust would be nice.

 

[Jasonmc]

You would need a rifled projectile...
Like a rifled slug for a smooth bore shotgun.. some shot good some didn't. Accuracy Was subpar at best. But close enough to get the job done..There's a reason even shotguns stated using rifled barrels. Your kinda wanting to reinvent the wheel... Use a rifled barrel of your choice and go with it... barrel makers already done all the work for ya anyway...

 

[CreationInk]

I dont think something like that would work.
You could Nozzle so the released air would be released in a way it would spin, but i think as soon as the pellet / ball are just a little away from the nozzle that spin effect would diminish as the pellet / ball get further and further down the barrel.
Now as you say if you could shape the projectile to be the nozzle that would spin air as it go thru the gap between pellet and barrel that would not loose affect, but i still think such a pellet would be hard to mold, and the loss of air would be undecidable.
Also as mentioned above i think it will be very hard to this way get the spin up to a number of RPM that is useable, here the grip of lands and groves are instant and the same from the very first mm of the shot to the last mm before the pellet leave the barrel.

Speaking of alternative, i just saw someone are planning to launch satellites with steam powered rockets, or at least steam powered 1 and 2 stages of the rocket.
Not that i am promoting steam rifles, just going alternative my brain remembered that.

FX old ST barrels is probably the most easy way, with just rifling the very last 2 inches of the barrel, work fine too, i have always been impressed with the performance of my FX Cyclone.

Hi Peashooter, thnx for sharing you're insights. You are correct, molding the slug that precisely would be hard, didn't think about that. Also

"FX old ST barrels is probably the most easy way, with just rifling the very last 2 inches of the barrel, work fine too"

this is a good alternative, thnx for your suggestion.

 

[Peashooter]

I think even after FX moved on to make barrels ( in the same way but with rifling all the way ) some shooters still held on to their old school ST barrels for a while.

It did freak me a bit that what is essentially a smooth bore barrel aside for the last couple of inches could shoot that good.
Mind you on those last inches they do still grip the pellet to spin it up, its not like in that way it is a " softer " approach to a fully rifled barrel.
But its also not like the ST barrels needed to grip the pellet harder, it is after all just a rifling pressed into the barrel from the outside, so in profile i assume more like octagonal barrels than traditional hammer or cut rifling that have sharper transition between lands and groves.

 

[Peashooter]

I have also seem some pellets with a rifling like pattern on the skirt, but i think that was just a fab CUZ not very many do that these days, so probably no gain in doing that just a additional tooling cost.

 

[MartyMcFly]

I have also seem some pellets with a rifling like pattern on the skirt, but i think that was just a fab CUZ not very many do that these days, so probably no gain in doing that just a additional tooling cost.

The RWS pellets have that striation on the skirt, but I always thought it had more to do with them trying to control the stretching/ballooning of the skirt under pressure, at least that’s my guess.

Anyways, if someone wanted a pellet that self stabilizes beyond the natural Diabolo’s abilities it’s feasible to alter the head into a shape like those Nerf Footballs that were sold when I was a kid. It imparts a good spin.

-Marty

 

[CreationInk]

The RWS pellets have that striation on the skirt, but I always thought it had more to do with them trying to control the stretching/ballooning of the skirt under pressure, at least that’s my guess.

Anyways, if someone wanted a pellet that self stabilizes beyond the natural Diabolo’s abilities it’s feasible to alter the head into a shape like those Nerf Footballs that were sold when I was a kid. It imparts a good spin.

-Marty

View attachment 419660

Hi Marty, great suggestion, I like this

 

[Gerry52]

Hi Peashooter, thnx for sharing you're insights. You are correct, molding the slug that precisely would be hard, didn't think about that. Also

this is a good alternative, thnx for your suggestion.

FX made Original Smooth Twist, Smooth Twist & Smooth Twist X barrels. The Original Smooth Twist barrels were the ones with rifling only at the last 3 or 4 inches. Some of the most accurate pellet barrels ever made. Not so great with slugs. Luckily for me I have 3 of those guns.

 

[thomasair]

You don't really need any twist to do just fine out to 50 yards. I have a completely smooth barrel that shoots reliable 3/4" at 50. Plenty for most people's requirements. It might shoot well even further but I haven't tried it past 50.

Mike

 

[Peashooter]

Indeed. with pellets and their brake parachute / skirt, you can do just fine with a smooth bore

 

[FelixS]

My

...

FX old ST barrels is probably the most easy way, with just rifling the very last 2 inches of the barrel, work fine too, i have always been impressed with the performance of my FX Cyclone.

My Bobcat with the ST barrel was a laser. I did not know that it was only rifled at the end. Interesting.

 

[Peashooter]

I did not know

You can screw off the outer end, not just the protection for the moderator thread, and reveal the part with the rifling pressed into it.

Someone might need to do some bluing repair.

 

[Vana2]

My FX Royale 500 has the smooth twist barrel and it's definitely a keeper!

Interesting thoughts. The helical vanes on an arrow do a good job of stabilization but that's not something you can fit ito a typical airgunbore.

Military artillery sabotted projectiles sometimes have fins and rockets often have fins that pop-out but then again there's the issue of scale.

You might figure out a new way of stabilizing a small projectile but unless it's a "game changer" (God, I hate that overused expression!) it's not going to change the established norm.

Good luck with your project!

Cheers!

 

[CreationInk]

My FX Royale 500 has the smooth twist barrel and it's definitely a keeper!

Interesting thoughts. The helical vanes on an arrow do a good job of stabilization but that's not something you can fit ito a typical airgunbore.

Military artillery sabotted projectiles sometimes have fins and rockets often have fins that pop-out but then again there's the issue of scale.

You might figure out a new way of stabilizing a small projectile but unless it's a "game changer" (God, I hate that overused expression!) it's not going to change the established norm.

Good luck with your project!

Cheers!

Hi Vana, thnx for sharing your thoughts. I think for small scale (helical) groves would definitely be easier then fins. Maybe a combination of spinning airflow and groves on the pellet/slug. Also, this is just for fun, as I'm fascinated with how airguns work. Its truly a mechanical art piece in my opinion, especially semi-/automatic airguns.

 

[Vana2]

Hi Vana, thnx for sharing your thoughts. I think for small scale (helical) groves would definitely be easier then fins. Maybe a combination of spinning airflow and groves on the pellet/slug. Also, this is just for fun, as I'm fascinated with how airguns work. Its truly a mechanical art piece in my opinion, especially semi-/automatic airguns.

You're welcome

Fins that deflect air and airfoils that produce lift could create a rotational force to spin a projectile, whether it would be enough to stabilize it would be another matter.

Don't think that grooves would have any (useful) affect as they would be lost under the boundary layer of the airflow. By guess, I'd say that they might produce a bit of turbulence and drag at the most.

Projects are fun (I'm working on a homemade slug swaging press at the moment) enjoy yours!

Cheers!