Projectile Weight/Rifling.

Discussion/suggestions of research/experimental topics in armature development
Post Reply
Zynmaster
Posts: 4
Joined: Tue Aug 09, 2022 8:56 am

Projectile Weight/Rifling.

Post by Zynmaster »

Hello,

This idea has been brought up before in the past during the release of the prototype SGP-34 Coilgun. When I received the weapon, The first thing I’ve noticed was the weight of the projectiles. In my opinion, The reason the gun failed in terms of lethality was bullet drop due to gravitational down pressure. The suggestion I had in mind was to fabricate some projectiles using lighter materials in hopes of increasing speed without modifying the coils themselves or increasing power. But then again, I understand other factors play apart in speed also. Rifling the barrels, aerodynamics, X amount of power distributed throughout the coil. It does sound good in theory though.

I’d much appreciate any feedback.
arcflash_admin
Site Admin
Posts: 12
Joined: Mon Aug 08, 2022 8:53 pm

Re: Projectile Weight/Rifling.

Post by arcflash_admin »

The SGP-34 was the lowest power coilgun we've ever built. It was really an exercise in cost reduction more than anything.

Using lighter materials unfortunately doesn't make the rounds go faster.

In a pressure-based system like a firearm or an air rifle, lighter projectiles have the same amount of gas pressure exerted on a lighter weight. F=ma. Mass goes down, force stays the same, acceleration must go up.

In a coilgun however, the force is proportional to the magnetic saturation of the armature. And the saturation is proportional to the density of ferromagnetic material inside the bore. When a lower proportion of that armature is steel (because you need to remove steel to make it lighter), you actually get *less* force. F=ma. Mass goes down, force also goes down, acceleration roughly stays the same. So now you have a lighter projectile traveling at roughly the same speed as before. It's going to be even less effective.

Coilguns are most effective with large heavy projectiles. Graviational drop will always be a concern, but I think as the technology evolves we will see coilguns becoming short range defensive weapons. Railguns and induction coilguns which can achieve supersonic velocity will be more suited to long range applications.
Zynmaster
Posts: 4
Joined: Tue Aug 09, 2022 8:56 am

Re: Projectile Weight/Rifling.

Post by Zynmaster »

I hope both coil guns and rail guns become EDCs and Sporting rifles. It’d make hunting and target shooting a lot more interesting. But what about aerodynamics? A smooth flight pattern of the projectile after leaving the barrel of the coil/rail guns?

I’m bringing this up because I’ve noticed from hands-on testing and review videos of the Anvil Railgun that the flight patterns of the projectiles lack a proper flight pattern and impact the targets differently. For instance, they flip through the air and impact the target differently with each shot. With the above mentioned, would it be possible to sacrifice small portions of steel from the dowels to improve the projectiles flight trajectory? And by small amounts, I mean enough to stabilize the rounds once in the air but not enough to interfere with the loss of force. In other words. Keep it heavy and also make it soar through the air better.
arcflash_admin
Site Admin
Posts: 12
Joined: Mon Aug 08, 2022 8:53 pm

Re: Projectile Weight/Rifling.

Post by arcflash_admin »

Yes, there are a few ways we've considered doing rifling.

The main objective is keeping the ammunition low cost. Complex geometries, finned projectiles, etc. all bring the price up dramatically for the end user. Requiring complex ammunition to impart spin also disallows users from making their own ammunition from bolts and scrap.
Zynmaster
Posts: 4
Joined: Tue Aug 09, 2022 8:56 am

Re: Projectile Weight/Rifling.

Post by Zynmaster »

Ok, Keep the ammunition low cost while maintaining the ability for the users to craft ammunition. That gives me another idea but I’d have to test it personally. This is off topic but does this thread permanently stay up or does it delete after so many days or weeks?
arcflash_admin
Site Admin
Posts: 12
Joined: Mon Aug 08, 2022 8:53 pm

Re: Projectile Weight/Rifling.

Post by arcflash_admin »

I think posts remain on the board permanently unless you delete them.
Zynmaster
Posts: 4
Joined: Tue Aug 09, 2022 8:56 am

Re: Projectile Weight/Rifling.

Post by Zynmaster »

Update: I have a design and formula sketched out for a muzzle attachment for the SGP that I’ll begin constructing once I get the materials needed.
kermudjin
Posts: 2
Joined: Thu Sep 01, 2022 11:19 pm

Re: Projectile Weight/Rifling.

Post by kermudjin »

I just discovered your coil gun product from a post on OffGrid magazine. What a cool device!

But I wonder if instead of rifling the barrel, you rifle the projectile? Nothing fancy. Use twisted steel galvanized deck nails, cheap at your local box store, cut down to size. Have you experimented with these as projectiles? Will the twist in the steel be sufficient to get the projectile spinning due to air resistance in the barrel before it exits the muzzle? It would presumably also add inflight stabilization, without meaningful drag, if you cut the nailhead off before using. The pyramidal nail point would also perhaps lessen tumbling and improve aerodynamics, as well as target penetration, thus requiring less muzzle velocity.

Sci-fi books often describe “needler weapons” that rapidly project multiple flechettes at high velocity to shred a target with tiny projectiles. But decking nails could potentially be the working man’s flechettes. ;-)

Just a harebrained thought from a clever old fart who loves to tinker…
Last edited by kermudjin on Fri Sep 02, 2022 12:04 am, edited 1 time in total.
kermudjin
Posts: 2
Joined: Thu Sep 01, 2022 11:19 pm

Re: Projectile Weight/Rifling.

Post by kermudjin »

The more I ponder it, the more I think this could be the ideal home defense and varmint control weapon. Precision accuracy is not needed at PDW range, and it would be easy to train loved ones how to use it effectively. Nails at 200fps are not going to get far through walls, making it a relatively safe in home weapon. But a spray of nails to the face and torso of an attacker would disable them fairly quickly, no? Ditto for rats and varmints. And you could practice with it in your backyard without upsetting neighbors!

You would need a redesigned magazine to hold several dozen trimmed nails, so spray and pray shooting could be effective. But I wonder if designing the weapon to use nails instead of your cylindrical slugs could be more efficient with cheap, light projectiles, making the weapon even lighter and faster.

I have an automatic CO2 powered BB gun that is a blast to play with, but only a toy, definitely lacking the lethality or penetrating force of an electromagnetic nail gun. I also have sundry other traditional firearms, but they are too noisy for backyard practice where I live.

Find a way to shoot nails, and I would become a customer!