Improving darts - some thoughts

[scottcrete]

a real at4.. by the way.. can only hit a targeted target at 300 meters and that is with a good aim.. the thing will fly over a mile.. but will only hit a target up to 300 meters

you think you can do it with a spudgun....

ha ha ha ha......
thats all i got to say..
If a rocket powered missile cant stay on track for that far.. what makes you think a air driven dart will? i mean be honest..

Maximum effective range: 300 metres (984.3 feet), although it has been used in excess of 500 meters for area fire.

[Ragnarok]

@scottcrete: Was that tone really necessary? You don't need to treat me like a half-wit.

I don't know about your mechanical background, but I'm a university student with a heavy grounding in physics and engineering, a heap of spudding experience, and I've got some brains - so usually I'm more accurate with my predictions than most people are.

I never said I was certain that it could be done, but certainly I do think there's a chance. Also, I think you might be assuming I'll be using a run of the mill launcher... oh no, certainly not. I can easily put paint-balls through steel plate with HEAL, and that was at well under the pressure I'll be using for the darts.

Now, on to what you said...

The comparison to an AT-4 isn't a great one. Any projectile that uses rockets or other similar means to propel a projectile outside a barrel risks inducing instability, because a force is being applied towards it's centre of mass.
Few unguided rockets are likely to be much good outside a few hundred metres, especially one shot disposable weapons.

A drag stabilised dart is a completely different kettle of fish. If you have to compare that to something military, I'd suggest something like a APFSDS kinetic energy penetrator, essentially what my design is based on, which are capable of accuracy into many miles, and hundreds of feet of projectile drop.

A dart from a spudgun, although clearly not the equal of such designs, and launched at lower velocities shouldn't be too hard pressed to be able to create workable (if not perfect) groupings at relatively long ranges.

Now, would people please stop posting comments that say it's impossible/near to impossible?
I know it's going to be far from a walk in the park, but I'm allowed to have my dreams, aren't I?

[Blitz]

I have no doubt in my mind it can be done. No less by you.. 8)

I favor the PVC fins, provided they're very thin. I'm sure that's what you had in mind though.

Very interesting reading though, I read this entire thread at least twice already, and if I were in a position to help, I'd offer it!

[Jared Haehnel]

I'm going to agree with Blitz PVC fins would probably be the easiest way to go...didn't you mention that you could cut plastics pretty accurately?

Sorry if I sounded like I'm trying to crush your dreams....I'm not...I am just interested to see how you will over come some of the challenges involved...like the Blitz above siad if any one can do it its you...

[Ragnarok]

Sorry if I sounded like I'm trying to crush your dreams...

No problem, I'd just rather not hear repetitions of the same things over again - of course, if anyone sees a problem that hasn't yet been mentioned, please do mention it.

The fins will be either 1.5 or 2mm thick, as those are the thicknesses of PVC sheet I can easily get.
Haven't decided which yet, each will have advantages, and disadvantages.

[jonot05]

I know this is quite a a late post, but i'd just like to ask whether or not you expect your dart to go supersonic? The .22lr is amazing cartridge which from experience is capable of accuracy out to about 110m-120m using "high velocity rounds. After this the accuracy drops considerably because the projectile goes from supersonic to transonic. This causes turbulence because of he projectile being overtaken by it's sound waves.
Solutions: Make sure your projectile will not go transonic until it has passed the 500m mark
Or
Make sure it does not go supersonic.

Your neighbors will love you if you do the 2nd option
Jono

[Ragnarok]

Make sure it does not go supersonic.

That was the plan. I was hoping for about 900 fps, which is about Mach 0.80, safely below the transonic range for this dart shape, but fast enough the trajectory is reasonably flat. With the dart's predicted drag characteristics, it should be able to make the planned 400m distance with less than 1.6 degrees of elevation.
A lot in firearm terms, but not so much in airgun or spudding terms.

Your neighbors will love you if you do the 2nd option

I won't be able to do this anywhere near my house, there's simply not the room.

[jonot05]

900 fps is very respectable given the mass of a dart. The 510 whisper round is a subsonic sniper round with 1MOA grouping at 500m. This is probably the rifle round most comparable with a dart.
If they can do it so can you.

[VH_man]

I think the use of Playing darts is extremely phesable. Expensive, but Phesable.

Better yet, i think the use of commercially-made blowgun darts is a better option.

[Ragnarok]

900 fps is very respectable given the mass of a dart.

The planned weight is about 12.5 grams, a little less than half an ounce. The ME will be of the order of 330 ft-lbs.

The whisper round does have rifled barrels - although my dart design will have it's own accuracy features.

[ALIHISGREAT]

interesting thoughts, although the problem i see with your plans is consistent darts... although i look foreward to seeing you hit a 5"x5" target at 500 yards.... oh and the other problems... where will you find 500 yards to shoot? and you will need alot of consistent darts in order to sight in your cannon... which is even harder than making a few consistent darts

oh and and pics of your dart design?

[al-xg]

People have hit targets with an airgun @ 512yards using a boat tail bullet.
CTC grouping with 6 shots was 12.25 inches though... but thats considering the shooters accuracy too.
Another guy managed to hit a 3L water bottle at that range.

I even hit a target 218yards away, with a 14mm roundish lead ball with my unfinished canon, although the accuracy wasn't great, but i was shooting standing up with no sights...

So the range should be achievable, but then for penatratindg 1/4" steel at that range...
I haven't tried steel plate penetration with a good preojectile in a while, and when I did, didn't have a powerful canon.
But I do know that the lead balls don't penetrate 1/8" even at a few yards... but then again, they're lead, round and 14mm wide...

[Ragnarok]

although i look foreward to seeing you hit a 5"x5" target at 500 yards....

Most likely, I will scale back to 400 metres. I'm working on finding a venue.

and you will need alot of consistent darts in order to sight in your cannon... which is even harder than making a few consistent darts

Not as many as you might think. I'll need a few darts for velocity calculations and zeroing at shorter ranges, then from there, I'll use the data to calibrate my range calculators.

And consistency may not be quite as necessary as you think. If you can get a sufficently high ballistic coefficient (we are talking outside the range of normal bullets though), then changes in the drag coefficient of the order of 10% will only have minor effects on impact point at 400 metres - we're talking maybe a couple of inches in this case.

Now, I can't predict the exact drag co-efficent of any round before it is fired. However, if we assume it to be approximately equal to all the other rounds, POI won't be affected by more than a couple of inches.

Variations in round weight and velocity are another matter. If I can control the cannon's pressure accurately, and run a few calibration shots, measuring the projectile mass first, then work out exactly how projectile mass affects the launch velocity, I can compensate for projectile mass variation before it's even fired.

oh and and pics of your dart design?

Which one? There are several.

@al-xg: Well, the good thing here is that the dart's whole aim is to penetrate - both air and steel, so they're not too far separated from each other.
There will have to be some compromises - ballistically, a fast long nosed dart is rewarded (flatter trajectory), but for penetration, a heavy and solid dart is better - and fins could get in the way.

The solution here is to have a dart with the longest nose I dare, and as long and narrow as I think can still be stabilised - with fins designed to break free on impact.
And of course, a dart with a hardened tip.

@VH_Man: Sorry, didn't see your post last night.
Blowgun darts have very high drag, and simply won't be able to make the distance.
Playing darts are much too heavy for a really decent velocity - and again, their drag characteristics aren't ideal for longer ranges.

Not to mention I don't think either would want to go through plate steel.

[al-xg]

Well you only need just over 1/4" before reaching the fins in theory.
I'm sure anyone would be happy if you get a clean hole, the fins breaking off is just a bonus against steel plate, just get the nose through

Although with pointy projectiles, there is still quite alot of friction even past the nose as the hole, is jsut the right size.

But have you put holes though 1/4" steel already, at close range ?


Actualy come to think of it, even my first ballvalve gun did actualy penetrate that 1/8" steel plate, but using 36g steel nails.
Also I'm forgeting the lead balls were shot using only 80cc of chamber volume.
Are you planing on using a single shot canon ?

So now my only concern is accuracy

[Ragnarok]

But have you put holes though 1/4" steel already, at close range?

Not yet, although I believe the launcher should be up to it.

Are you planing on using a single shot canon ?
So now my only concern is accuracy

The dart design is being optimised for 3vo, which will be able to operate in any of a number of ways. Most likely, I'll be using the single shot manually cycling option.

We'll see how the accuracy works out.