Since I have some rifle barrels which are either shot-out, or have oversized bores, the thought occurred to me that these might be resurrected cheaply by reaming out the rifling and then use fin-stabilized projectiles in them—like a tank.  I’m thinking along the lines of a heeled sabot containing a fletchette type projectile.  The bore would be reamed and polished to about the same diameter as the neck part of the chamber. Such a musket would be for target use—hopefully serious target shooting.

The advantages would be: 1) high velocities without high pressures due to a larger piston area, lower friction (depending on sabot material), and low mass projectile including the sabot; 2) no worries about throat erosion affecting accuracy; 3) easy to clean; 4) easy to produce high quality barrels for EOTWAWKI.. 5) good ballistic coefficients are practical. 6) light armor piercing, though I see no real need for this in a caliber .30 or smaller weapon.

The disadvantages would be: 1) projectiles would not be suitable for hunting game; 2) making good projectiles and sabots cheaply might be difficult; 3) California (and, perhaps, other states??) law prohibits fletchettes in firearms; 4) accuracy is an unknown and it may be impossible to attain the target level of accuracy wanted.

The questions I have are: 1) what fin design and how many fins would be best for muzzle velocities in the order of 5000 fps; 2) what material for the sabots (Delrin, PTFE, wood, UHMW, etc).; 3) do I make a mold and cast the projectiles out of lead alloy, or make them out of steel; 4) if steel, one piece, or make the fins attach separately. 5) has this been done and what kind of accuracy has been attained. 6) would it be legal for high-power matches.

Any thoughts would be appreciated.

Pic of concept below.

Sounds like a good place to pour some money…

I do not think you will be able to achieve 'match grade accuracy' but it could achieve hunting use with tumble/fragmentation.

I expect projectile manufacturing would be the expensive part, in order to make a successful design that is cheap to manufacture. The mass fletchettes used in artillery rounds were stamped out by a nail manufacture. Tank rounds are machined with multiple processes an assembly.

But before worrying about manufacture, you need to settle on a design that will reach your goals.

I would also pass this by the BATF to make sure you are not violating any rulings. I am guessing it would be a 'shotgun' in their eyes since it is not rifled.

About the closest small arms match would be the 12-gauge shotgun using Sauvestre fin-stablized discarding sabot slugs for deer hunting.

Otherwise you've got some work and expense ahead.

www.sauvestre.com/index_us.htm

O.K. I'm going to bump this to see if I can get more responses, and at least more reads---different crew, perhaps.

Dave

i would guess the AP potential will make this illegal

Quoted: i would guess the AP potential will make this illegal

If the projectile were cast of a lead alloy like electotype or linotype, I don't think it would be very usefull as AP.  Also, are there any federal law which prohibit AP projetiles?


I'm cuious as to whether anyone here has actually tried anything like this.  Google searches gives some vague articles about such things, but no experimental data that I can find.

As far as expense, It would be easy for me to bore out a barrel, and fairly easy to make the projectiles or even a mould.  The sabots may be a bit harder to do.  I'm most interested in what kinds of designs have been tried---if any.

Dave.

It's been done before and was a commercial failure.

google "Remington Accelerator".

If you design a good fin-stablized discarding sabot you'll have a winner.

Quoted: It's been done before and was a commercial failure. google "Remington Accelerator". If you design a good fin-stablized discarding sabot you'll have a winner.

That is exactly what I had in mind.

The accelerator required spin stabalization imparted on the sabot and subcaliber bullet.  I remember the concept well.  

What I need, is ideas on what constitutes a good sabot, and projectile---principally the fin design.  That is, should the fins be tapered or square relative to the shaft; how much should they stick out beyond the diameter of the shaft (1, 1-1/2, or 2 diameters); three fins or four, or more; etc.?

Should I design the sabot by copying what is used in our current tank, or is there a better design for smaller calibers.  I'm not sure how compressible fluids (air at supersonic velocites) flow around various shapes.  Thus, I don't really know how to design a sabot that will break-away without disturbing the core projectile.

These are some of the questions I want some help with.

Dave.

The "Accelerator" and miltary ACR and a few other tests used rifled barrels and a production bullet in a plastic sabot.  They achieved high velocity, and accuracy was on par with full-bore ammo.  

The big problem with the "Accelerator" rounds was Remington marketed them as varmit bullets you could use in your normal hunting rifle, and since they gave the same accuracy as a full-boare round, if your hunting rifle in .30-30 gave you 3" 100yd groups, your "Varmit" ammo was going to give you 3" 100yd groups.  That's NOT varmit ammo.  So sales sucked big time because they simply didn't do anything you couldn't do with the nomal ammo.  If they didn't improve accuracy, I would have the same chance of hitting a critter with a 30-30 round than an Accelerator.  Why bother paying the premium for ammo that didn't do anything for me?  It's basically a solution for a non-existant problem.

The military uses SLAP rounds in .50s.  They tried them in 7.62, but had problems with bullets coming out the side of barrels, etc. though I don't know the actual reason for the problems.  The .50 SLAP is the smallest they use.  

The best thing for you to do is start some research by looking up the SPIW.  That was an Army program that built a flechette shooting rifle.  "SPIW" "Serial Bullet Rifle" and "ACR" might help as well.  The Army's already done most of the experimenting on them that there is to do.  I'd start by looking at some of that stuff first.

There was also another project in the 60's that used the "Tround" concept of the Dardick pistol (actually the Dardick used the project's principle).  It was an open chamber, externally powered gun that used a flechette in a plastic sabot that was in a plastic triangular casing.  It was for aircraft use IIRC, or at least the original program was.  While the Dardick just used a bullet in the Tround, I remember looking at pics of the project and this one used a sabot and flechette.  This was back during Vietnam and "Project Beehive" when the military spent a wad of cash on flechette technology.  

The obvious comment though is it would be a helluva lot cheaper to rebarrel the gun than go down this path.

Quoted: *snip* The obvious comment though is it would be a helluva lot cheaper to rebarrel the gun than go down this path.

True, but I have the ability to do the work myself, and I am an experimenter at heart.  It seems different enough that before I rebarrel these rifles, I may as well try something with the old ones first.

And thanks for the info on the Army projects.

Dave.

Quoted: Quoted: *snip* The obvious comment though is it would be a helluva lot cheaper to rebarrel the gun than go down this path. True, but I have the ability to do the work myself, and I am an experimenter at heart.  It seems different enough that before I rebarrel these rifles, I may as well try something with the old ones first. And thanks for the info on the Army projects. Dave.

If no one ever tries anything new, nothing new gets invented.  I say go for it if you want to try it.  If it becomes too much, you can always rebarrel it later anyway, so it's not like anything bad can result.

1) FDS ammo is best for shotguns...

2) Yes, it should be possible to make a 'miniature' APFDS round within the federal guidelines for ammo composition... Especially in a shotgun, where the sabot would be a large portion of the bullet mass....

3) It would be expensive as hell - that's why APFDS is limited to government applications now - COST...

Quoted: 1) FDS ammo is best for shotguns... 2) Yes, it should be possible to make a 'miniature' APFDS round within the federal guidelines for ammo composition... Especially in a shotgun, where the sabot would be a large portion of the bullet mass.... 3) It would be expensive as hell - that's why APFDS is limited to government applications now - COST...

I'm not sure that it would be all that expensive.  Once the design is figured out, and appropriate moulds made, the projectiles shouldn't cost more than premium bullets.  I mean, steel wire (even drill rod) is rather cheap since I would be using something like an 1/8 inch diameter or smaller, and casting a lead alloy profectile is really cheap.  Also, Once the mould is made for the sabots these should cast very inexpensively.  Think about  shotgun sabots in minature---not much material.  Besides, the machine work I can do easily.

Dave.

Would a lead alloy projectile work as a fin-stabilized penetrator? Or do you meant to use a lead projectile for a more conventional saboted projectile? Would an unjacketed lead projectile fly apart at the velocities you've mentioned?

Quoted: Would a lead alloy projectile work as a fin-stabilized penetrator? Or do you meant to use a lead projectile for a more conventional saboted projectile? Would an unjacketed lead projectile fly apart at the velocities you've mentioned?

Sure.  The lead projectile would work as a fin stabalized when cast in the general shape of an arrow.  And, since it is not really spinning (though I think it might help if the fins imparted a slow rotation) it won't fly apart.  I'm not thinking of using a normal lead bullet shape, nor that of a shotgun slug either.

Dave.

Here is a picture of my idea.  I have not included any dimensions since I have not yet worked out the details.  It is just a concept at this stage.  If anyone has any specific ideas on how to  design any components, I would be appreciative.





Oooh. My first Pic. and it seems to work.

Dave.

I think that assuming a metallic flechette might be a mistake. I think the best material would be a ceramic core and top jacketed in copper. A ceramic matrix material is cheap and once molds are created easy to produce in large numbers without sophisticated tooling. Also ceramics are relatively light as well as harder then most metals. This will give the flechette superior penetration against armored targets as well as better terminal ballistics since that the tendency for a flechette type projectile is to 'fish hook' in dense tissue causing, frankly bizarre wound paths, as was found out during the SPIW and ACR programs. With a jacketed ceramic core flechette once the round has penetrated tissue it will shatter when dynamic pressure causes the shaft to yaw. This will impart the maximum amount of energy to the target without loosing penetrating ability.  


I think this kind of projectile has a huge amount of potential, especially if you coupled it to a unitary polycarbonate sabot and self consuming primer you could end up with an essentially caseless round so you could bypass the extraction phase of the firearm. Since you wouldn’t have to worry about ejecting spent cases you could configure the rifle as a bullpup without having to worry about mechanically solving the weak-hand shooting issue.

Quoted: I think that assuming a metallic flechette might be a mistake. I think the best material would be a ceramic core and top jacketed in copper. A ceramic matrix material is cheap and once molds are created easy to produce in large numbers without sophisticated tooling. Also ceramics are relatively light as well as harder then than most metals. This will give the flechette superior penetration against armored targets as well as better terminal ballistics since that the tendency for a flechette type projectile is to 'fish hook' in dense tissue causing, frankly bizarre wound paths, as was found out during the SPIW and ACR programs. With a jacketed ceramic core flechette once the round has penetrated tissue it will shatter when dynamic pressure causes the shaft to yaw. This will impart the maximum amount of energy to the target without loosing penetrating ability.

But, being a less dense material, it would be harder to maintain good ballistic coefficients.  The primary interest I have in this is punching holes in paper, specifically within the x-ring.  Armor piercing, however, does have some interest.

I think this kind of projectile has a huge amount of potential, especially if you coupled it to a unitary polycarbonate sabot and self consuming primer you could end up with an essentially caseless round so you could bypass the extraction phase of the firearm. Since you wouldn’t have to worry about ejecting spent cases you could configure the rifle as a bullpup without having to worry about mechanically solving the weak-hand shooting issue.

Couldn't one ignite the propellant charge with an electric spark?  Also, wasn't this idea essentially explored with the Tround?  I'm not saying that there may not be other ways to approach the concept, it's just that for my purposes at the moment not what I want to delve into.

Dave.

ETA.  Also, why polycarbonate for the sabot, rather than HDPE, or other plastic.  Doesn't polycarbonate have a higher coefficient of friction on steel than other less expensive and more easily formed plastics?

ArimoDave,
Your concepts are almost identical to ACR cartridges from the late 80's.  The Colt version looks just like your pic.  5000fps with a 10gr flechette.  Accuracy was ok, but problem was that wounding was minimal.  Flechettes will zip right through a body without the person even realizing he was shot.  Findings were that if the flechettes were differentially heat treated (hard at the tip, soft shank), penetration was adequate and the flechettes would bend ("fish-hook") and tumble, doing a bit more damage in soft tissue.  Good news is that soft body-armor is paper to a hi-vel flechette.  Steyr had a bullpup rifle with a plastic-cased cartridge with a 6200fps velocity!!  The rifle had a 4 or 6 MOA illuminated donut reticle sight which would give a direct hold on a human target out to 600m.  
Long story short, neat idea, but real world physics proved that conventional bullets and quality firearms are cheaper and more effective.  Lightweight hi-vel flechettes are effective against soft body armor, but not much else.  Flechettes do nothing against brick walls or auto bodies, and terminal effects are crap.

Peter Kokalis did extensive testing on these for SOF and other sources.  I can't cite specifics right now, but i could.

As to your specific requirements (target shooting???), accuracy was mediocre at best, but drop is minimal, due to high BCs.  Wind drift is excessive, though, so long range shooting is probably iffy.  Adding a saboted projectile just makes a complicated equation (long range target shooting) worse. You can ignite a powder charge electronically, and it makes lock time essentially zero, but that minimal advantage is heavily outweighed by the inaccurate tendencies of saboted ammuntion.  Remington produced an electronically fired version of .223 ammo with the advantages of electronic ignition, and Voere produces caseless electronically fired ammo/rifle combos which do well, but still, quality conventional ammo/rifles is still superior.

I encourage you, because I think along the same experimental lines as do you, that if you have the means, please experiment.  And report back any findings, because I would like to learn of any developments.

I think some flechette submunitions had a tendency to turn into a fish hook shape when getting into liquid/tissue medium which resulted in better terminal performance.  I don’t know what design considerations are required to achieve this effect rather than the problematic zipping right through but I read about it during the ACR trials IIRC.

Quoted: ETA.  Also, why polycarbonate for the sabot, rather than HDPE, or other plastic.  Doesn't polycarbonate have a higher coefficient of friction on steel than other less expensive and more easily formed plastics?

I don't have the numbers in front of my but I recall thinking that HDPE and most other high-temperature plastics would have a significant amount of their exposed material sublimed away by the heat and pressure of the detonating propellant deforming the sabot and adversely affecting accuracy. It was my understanding this is the reason why Steyr had to switch to polycarbonate sabots and cases on their ACR entrant.

Your correct, this kind of cartridge does lend itself to electrical ignition, unfortunately electric ignition presents some problems of it's own about supplying an integrated sustainable power supply. I actually played around with having a Faraday Effect coil operated by gas piston trickle charging a compact Lithium-Ion battery cell to provide power for electric ignition systems without having to worry about battery replacement. Making such a system work, while I'm sure is not impossible, is definitely tricky...trickier then I though although it does offer some accuracy and reliability improvements over mechanical ignitions if you could make it work.