SpudFiles

I know there has been tons of help me posts about trying to rifle a barrel. And it has always kind of ended if you can figure out how to do it make me some...

Perhaps a discussion on how to make more accurate ammo for a smooth bore would yield better results...

Theres a few approaches...shotguns use rifled slugs so if one could figure out how to rifle to out side of an object it would increase the accuracy... and would be easier to rifle the out side of the object then the inside....

Theres also finned objects...like arrows and rockets that could stabilize its flight...

paint ball barrels often put a back spin on the ball to create a more accurate shot ...

Is there some other ways that I haven't thought of? Any ideas of how to create pretty accurate ammo without rifling the barrel?

Jared Haehnel wrote:shotguns use rifled slugs so if one could figure out how to rifle to out side of an object it would increase the accuracy... and would be easier to rifle the out side of the object then the inside

the external rifling on shotgun slugs doesn't actually give the projectile significant spin. From this page:

Heavy external "rifling" was cast into these Foster type slugs, allegedly to allow the air they flew through to impart a slow spin that would help stabilize the slug. Like most something for nothing schemes, the rifling proved ineffective, but it did provide some space for some compression if the slug had to squeeze through a tight choke.

Rifled slugs are stable from a smoothbore barrel due to their hollow tail which gives it a forward centre of gravity, in the same way a spear flies straight.

The key to accurate ammo is consistency - rounds must be similar enough in shape, size and weight to give a predictable flight path.

So the accuracy is increased marginally through the stability...I.E it keeps the slug from key holing the target... which also would allow the slug to maintain a higher velocity for longer.

So one step, in making more accurate ammo would be to hollow out the base...

If rifling the outside of the object works only marginally it probably wouldn't be worth it unless you could case your own rounds... cheaply

A hollow base (as in this projectile from a CO2 12 gram capsule) will allow for stable flight, ie the projectile will be drag stabilised and will fly straight instead of tumbling end over end - but for accuracy, if you cannot manufacture the projectiles reliably to the same specifications then you'll never be able to zero your sights.

I guess we'd have to determined what kind of accuracy is appropriate..... 3 foot groupings at say 50 yards? Not looking for sights. If you did put sights on the best you could to is place sights similar to those found on a shotgun

That gives me an idea...cut a disposable C02 cylinder in half and put a marble or lead weight in the front... with a 3/4 barrel. Probably need some kind of wading though...

I've shot charged ones and taped a tack at the tip so when it hits the target it shoots off in a different direction (No, they don't explode)...kind of fun to watch but thats off topic... they have decent accuracy but I've never tested it before to see what kind of groupings one might get

several weeks ago I was trying to create rifled ABS barrel for 16mm marbles but it wasn't working working well...
I also tried to build a hop up - 10 to 15 cm of electrical tape inside the barrel are enough to put spin on marbles - last weekend I fired the whole pack of ammo with it and they were quite consistent... but honestly I get simmilar or slightly better consistency when using steel bolts as ammo...

long time ago I was experimenting with using nails as projectiles... the nailheads fitted nicely in 6mm barrel... I grinded them in order to move the center of gravity more to the front and they were suprisingly accurate... it seems that the nailheads were drag stabilizing them...

3 foot groups at 50 yards is poor accuracy even for an arquebus. With reasonably consistent ammunition and fill pressure, I would expect a pneumatic spudgun using rudimentary sights to reliably put all its shots within a one foot square target.

Using this launcher and firing tight fitting ball bearings I could easily hit a floppy disk at 20 yards.

OK so we can narrow the definition of accuracy to groups with in foot square...

Nial thats an interesting idea I hadn't thought of that... cheap easy to get and pretty accurate. Your right the nail head probably acts like a drag fin to stabilize the flight...great for small bore guns

I wonder what the difference is in the steel bolts?

bolts tumble in air... but their density is relatively high and as a result they are quite accurate (about 4 foot groups at 160 feets)

Anything that has weight in the front much heavyer than in the back will fly straight.

Ok so thats about 50 yards ...if the bolts flew straight without tumbling the accuracy would be increased significantly...

perhaps different length bolts of the same diameter would preform differently... same concept as nails though the head acts as a drag fin. Perhaps put a larger washer to increase the air of the fin?

Here's an idea I drummed up awhile ago for piant ball but it wold probable be better apllied to an oblonged shaped object...

You get the barrel spinning at a high rpm which would impart the spin on the projectile. Bullet spin in execess of 100,000 rpms so we couldn't replicated that kind of spin however I would think 3,000 rpms would be reasonable... would it be worth it? Probably not but for kicks and giggles... I would think it would help to stabilize the projectile and keep it from tumbling provided it was balanced.

Jared Haehnel wrote:You get the barrel spinning at a high rpm which would impart the spin on the projectile.

Creating a seal and bearing mechanism to make that possible would be hard.

Moving seals are difficult anyway, but creating a high rev moving seal that won't shoot forwards on firing, but is low enough friction for a practically sized motor to handle... it's going to be damned hard.

The moment you talk about any rotary part in a spudgun, you're going to have one hell of a time try to make it work.

Yep... thats why I said it wouldn't be worth it... but its an interesting to think about...

Just better focus on improving the accuracy or the ammo we shoot...

He's another random thought...how about attaching a couple fins at an angle behind but attached to an projectile... would that impart enough of a spin to amount to much?

@Jared you could insert bolts into a small piece of garden hose or pressure hose - I think this idea was presented here sometime ago... this way you could create a round with a hollow base... I never tried that but it might work...
I agree with ragnarok rotating barrel is a waste of time...instead you might consider getting some of those surplus military flechettes from behive rounds (JSR - link needed ) defienatelly it would be cheaper and easier than building a rotating barrel