Fin-Stabilized Discarding-Sabot Projectile Designs

[Matt304]

I have searched quite a bit for information pertaining to (AP)FSDS ammunition--pertaining to the projectile design specifics--yet I have had little luck finding much.

For example, the 25x137mm round would be there most desirable round to find data on, as it's the smallest cartridge which appears to have a very effective sabot design. The 25mm has multiple sabot projectiles, but I am speaking to the nature of the fin-stabilized type where the projectile looks like a dart.

I have seen high-speed footage of this similar projectile and the sabot design is interesting because the petals seem to lift away from the projectile before drag is able to get a hold of them.

It appears the rear of the sabot is designed to get a push right as it clears the muzzle from the high-pressure gases exiting, which seems to be how it obtains some of the energy required to split the sabot apart where the driving-band region is.

All I have been able to do is watch videos and sort of imagine the physics going on combined with the shapes of components to guess how they were designed to work, but I haven't been able to find the testing and specification data anywhere to know how the sabot is manufactured to specifically work.

I have wanted to perform some simulations in some of the flow dynamic software I have to try and possibly make my own design that works from a high-pressure 12GA FH. The FH (From Hell) has the powder capacity and muzzle energy capability to potentially mimick a scaled down version of such a sabot, with adequate bore size to have a fighting chance from the start. But to have an idea of what to scale down, it would be a wild guess without the data and specifications from something like the 25mm round.

I also wonder if--because of the aerodynamic stability produced by the fins--the sabot design is meant to impart spin from the rifled 25mm barrel as a form of added stability, or if the design allows slip to occur around the small dart design diameter relative to the bore size.

If anyone knows where to locate such data, it would be greatly appreciated. Thanks

 

[JTHunter]

Matt, I hate to tell you but the "dart" style of shotgun ammo is outlawed here in IL-ANNOY. As is the "bolo" style (wire connected pieces) and the "dragon's breath" firework round.
Check out the myriad of "not allowed" laws before you get in trouble by even possessing those rounds.

 

[Mk-211]

Two things to remember, you cannot have a muzzle brake on the weapon and if you're making it for a shotgun, I would also remove the choke.

If the sabot hits either of these it will result in a catastrophic end! That and possibly get you hurt in the process.

I have some sabot shotgun rounds for reloading, can't think of the name and would have to dig them out. They kind look like an ice cream cone with a flat base on it. Then the sabot is wrapped around that and then loaded into the shell.

If you're interested in buying/trading for them, PM me and we can work out something. There's 10 in the pack and if you don't use them, they might help you along in your idea.

I also have some for my 50 BMG rifle, these are the real deal! Not the aftermarket junk that people try to make work. When you see the design and learn how it works, you'll understand why they work better than the aftermarket junk.

 

[caribou]

Keep the projectile inert, as in no explosives and start "bigbore " with a very legal Black Powder cannon perhaps, and then refine it from there.

Spin, or more like 'rolling' with fin stabilized projectiles is normal, unless its using a HEAT type warhead where spin would disperse the explosive power, but thats not a problem for what your up top.

I cant think of a "fast spin, with fin stabilization, but RPG-7's (slow roll) and air to ground rockets come to mind.
You might look into smooth bore cannon types, such as used on tanks, in further research.
Researching Russian tank cannon would be a start, there should be quite a bit of info out there

 

[Jim Watson]

One approach in the SPIW program was 100" twist rifling, not for stability but for sabot separation.

 

[Archer]

I have searched quite a bit for information pertaining to (AP)FSDS ammunition--pertaining to the projectile design specifics--yet I have had little luck finding much.

For example, the 25x137mm round would be there most desirable round to find data on, as it's the smallest cartridge which appears to have a very effective sabot design. The 25mm has multiple sabot projectiles, but I am speaking to the nature of the fin-stabilized type where the projectile looks like a dart.

I have seen high-speed footage of this similar projectile and the sabot design is interesting because the petals seem to lift away from the projectile before drag is able to get a hold of them.

It appears the rear of the sabot is designed to get a push right as it clears the muzzle from the high-pressure gases exiting, which seems to be how it obtains some of the energy required to split the sabot apart where the driving-band region is.

All I have been able to do is watch videos and sort of imagine the physics going on combined with the shapes of components to guess how they were designed to work, but I haven't been able to find the testing and specification data anywhere to know how the sabot is manufactured to specifically work.

I have wanted to perform some simulations in some of the flow dynamic software I have to try and possibly make my own design that works from a high-pressure 12GA FH. The FH (From Hell) has the powder capacity and muzzle energy capability to potentially mimick a scaled down version of such a sabot, with adequate bore size to have a fighting chance from the start. But to have an idea of what to scale down, it would be a wild guess without the data and specifications from something like the 25mm round.

I also wonder if--because of the aerodynamic stability produced by the fins--the sabot design is meant to impart spin from the rifled 25mm barrel as a form of added stability, or if the design allows slip to occur around the small dart design diameter relative to the bore size.

If anyone knows where to locate such data, it would be greatly appreciated. Thanks

As it happens, I spent a couple of decades working with one of the designers of that very round, which was produced by Honeywell and later, ATK. There's plenty of data out there on "finners vs spinners", and even a company that made its bones on the modeling software (ArrowTech). There's a full suite of simulation software. The software is called PRODAS and you can inquire directly to the supplier, if you qualify. http://www.prodas.com/

 

[Shawn Dodson]

About 20 years ago I test-fired several Balle Flèche Sauvestre discarding sabot, fin stabilized 12 gauge shotgun slugs. Their accuracy wasn't that impressive. Here's a video link of somebody else testing them - https://www.google.com/url?sa=t&sou...Vaw0Tv9jkJzDfcQziAkk4eNS-&cshid=1593929965050

 

[CapnMac]

Some of that depends on the desired end-effect.
For armor penetration the projectile rod wants to be about 1:15 to 1:17, diameter to length. Materials science will give you a minimum diameter (IIRC, WO3 wants to be > 5mm diameter, or you have brittleness issues related to the acceleration.

The shoe is often near twice the projectile diameter; but the terminal projectile physics determine that. The 105mm APDSFS round used a 50mm diameter projectile; the 120mm round uses a 77mm diameter penetrator.

Making the shoe is another materials science exercise, you want light materials, preferably with a low coefficient of friction (or coat-able in such a material). You can bind the petals with a friable band, or a self-combusting one, or telescope the case (this is not often used). The base of the show typically gets a "cup" reminiscent of a gas seal used with lead bullets. That cup can be separate, or part of the shoe--it's almost always used to apply mechanical advantage to the petals of the shoe while obturating the bore.

The anti-armor physics is fascinating, as the penetrators resolves the PE/KE equations, the tip undergoes a state change and becomes an erosive plasma with considerable momentum to preserve, and all of the following mass of the projectile to influence the plasma wave front. This is where the length-to-diameter ratio kicks in.

Now, for "conventional" (for want of a better term) targets, the additional velocity DS provides is less off a mission requirement. The phenomenal accelerations can have their use, but even that is rather limited. This because you get into the argument of what "more better" do you get from a 50gr projectile at 4000fps that a 150gr projectile at 3000ffps cannot. There are targets where having an MV of 4/5 mile-per-second could be handy, the question becomes are those targets suitable for 40 or 50 grain projectiles.

So, it's probably going to be "niche."

Remington's short-lived X-cellerator rounds could be an excellent example. These probably should have been marketed as a handy way to turn a thirty caliber rifle into an impromptu "varmint" rifle. As they were using a 55gr cal.223 FMJ in a polymer shoe atop a .30-06; .308, or whatever the third one was, case. Instead, Remington just sold them as speed freaks. A way to get 3200fps out of 2600fps rifles, only without offering a good reason for "why" a person might want to. (Lack of projectile variety did not help much either--today a company would probably be inclined to use 60-70gr "varmint" projectiles.)

Shotgun, with its smooth bore is tempting as a mental exercise.