SpudFiles

I have an idea for a large artillery field piece. I am reaching out for help from the community because I have ran hundreds of simulations in GGDT and the best I have been able to get from my current design has been about 800 feet at 500 psig. Ideally, range should be about 600-700 yards, using pre-loaded cartridges. For the cartridges, I am thinking toolie pistons in a 3 inch sch 40 pipe that is reinforced on the outside by 3 inch couplings modified and hammered down the length of the cartridge. This allows more pressure and proper fit to the chamber and outer barrel, which is 4 inch DWV pipe.
Ammunition is going to be these: Nerf Howler.
Because the rules of the area i want to fire this cannon under, it most probably has to be a pneumatic. I will draw up some illustrations tomorrow.

Berkut wrote:I have an idea for a large artillery field piece. I am reaching out for help from the community because I have ran hundreds of simulations in GGDT and the best I have been able to get from my current design has been about 800 feet at 500 psig. Ideally, range should be about 600-700 yards, using pre-loaded cartridges.

Forget that sort of range using Nerf projectiles. The problem with a projectile for long range is that it needs to be good at "penetrating" the air - it needs to be of good aerodynamic shape, with a low frontal area and high sectional density - and these characteristics make it very good at penetrating flesh. This is why Nerf projectiles have the opposite characteristics, which makes them safe to use but very poor in terms of ballistic performance.

Also, hitting a point target at 600 yards is difficult enough with a rifle firing a streamlined dense projectile at three times the speed of sound, let alone with a subsonic foam dart. In order to make it realistic for use in a paintball or airsoft scenario, you would have to agree that everyone in say a 20 yard radius of the point of impact would be dead.

For the cartridges, I am thinking toolie pistons in a 3 inch sch 40 pipe that is reinforced on the outside by 3 inch couplings modified and hammered down the length of the cartridge. This allows more pressure and proper fit to the chamber and outer barrel, which is 4 inch DWV pipe.

If you plan on using 500 psi, I would be looking at stronger construction.

Also, why not burst disk cartridges? Easier and cheaper to make, lighter, faster opening time, zero flow restriction and air volume. No brainer in my view

Ammunition is going to be these: Nerf Howler.

If you stick with this, ranges beyond 150-200 yards would seem exceedingly optimistic.

I was hoping to get some input from you jsr.

If you plan on using 500 psi, I would be looking at stronger construction.

Also, why not burst disk cartridges? Easier and cheaper to make, lighter, faster opening time, zero flow restriction and air volume. No brainer in my view

I mentioned the 500 psi to demonstrate how inefficient the current design was, I don't really want to run it at such a dangerously high pressure.

I had thought of burst disks, but i have had problems getting them to seal with my launcher that uses burst disks. Maybe I'm just doing it wrong. :p

Also, hitting a point target at 600 yards is difficult enough with a rifle firing a streamlined dense projectile at three times the speed of sound, let alone with a subsonic foam dart. In order to make it realistic for use in a paintball or airsoft scenario, you would have to agree that everyone in say a 20 yard radius of the point of impact would be dead.

An agreed kill area would almost certainly be the case. The original idea was for area targets anyway. Additionally, the idea involved the use of forward observers to make corrections in targeting, and a lot of math.

As for ammunition, could a round be molded or cut out of foam? Mcmaster carr carries foam stock. Something more bullet shaped would probably work better.

I am also looking into methods of rifling the barrel.

Berkut wrote:I mentioned the 500 psi to demonstrate how inefficient the current design was, I don't really want to run it at such a dangerously high pressure.

Irrespective of how powerful the launcher is, the weak link as I pointed out as far as range is concerned is your chosen projectile. In any case, 500 psi from an efficient valve would likely tear the projectile apart in the barrel.

This is unavoidable though, if there's the risk of someone being hit it has to be low density. At least the Nerf has a decent aerodynamic shape.

I had thought of burst disks, but i have had problems getting them to seal with my launcher that uses burst disks. Maybe I'm just doing it wrong. :p

You could take advantage of the spongy nature of the projectile to do away with the burst disk altogether, and just have a friction ring at the breech against which the projectile seals against until the pressure buildup is big enough to pop it out like the proverbial champagne cork.



In this case, the cartridge would not contain any air pressure at rest. What you would do is have an air source and valve on the launcher, load the cartridge, hook it up to the air source, open the valve, *pop*, rinse lather repeat. In this case the valve could be anything really, even a simple ball valve or blowgun. The important thing is that it recloses quickly when you release it after the projectile is fired, in order to avoid wasting air.

An agreed kill area would almost certainly be the case. The original idea was for area targets anyway. Additionally, the idea involved the use of forward observers to make corrections in targeting, and a lot of math.

I think you might be a little optimistic here, even if you have a consistent launch velocity and reliable way of determing exact launch angle and bearing, there is the weather to be considered, and again the nature of the projectile means it will be extremely vulnerable to even a slight breeze. This would be exacerbated by high launch angles.

As for ammunition, could a round be molded or cut out of foam? Mcmaster carr carries foam stock. Something more bullet shaped would probably work better.

There are tons of ways you could make a projectile that flies further, but this would be to the peril of anyone in the impact area. I would stick with the Nerf, using a commercially available projectile at least guarantees reasonable confidence in consistent shape and weight.

I am also looking into methods of rifling the barrel.

Not necessary for a fin stabilised projectile.