9 replies to this topic

[steadyon]

Barrel rifling. Its been tried, failed, tried again, failed again.

People argue on for days, months, years about dart/barrel fit with rifling, friction on the dart, and effective ways to rifle a barrel.

I have a very simple answer as used on the persuader. Imagine you are making your stefans, when you put a hole in the front with your hot glue gun for the weight, do the same to the rear of the dart.

This way, as the air pressure forces the dart down the barrel, its effectively pushing this "skirt" into better contact with the rifling. Thereby imparting spin, without the drag associated with more pronounced rifling.

Diagram.




Flame on!

[Blue]

It's been done many times before, and people have gotten mixed results. From my experience, putting a hole in the back doesn't seem to do much.

[AJ R]

See next post... not used to the way the forum works yet. Sorry, all.

Have a sizzlin' day,
AJ

Edited by AJ R., 20 February 2010 - 03:40 AM.

[AJ R]

I actually pursued this... not worth doing, it just so happens. By making a barrel with rifling, the foam dart catches on the rifling... on top of that, the friction of the barrel is enough to hold the dart in place, keeping it from spinning. So all you would really do is lose air from around the dart.
My idea was to have a primary barrel and a secondary barrel... the secondary barrel being at the front of the gun and much looser than the primary barrel... and having the rifling in that. The idea was that the air would follow the path of least resistance, which would be through the wider spaces. If those spaces are in the rifled pattern, it effectively puts a spin on the dart without the issue of friction. The problem is that it is next to impossible to achieve axial stability with a foam projectile.

So, for one, it's kindof useless one way or another.

But I can definitely appreciate the ingenuity here. I like the idea of having a chamfered hole so the foam loses strength the closer to the back of the dart you get. Definitely an interesting concept, unluckily it still causes more friction than is necesary, and you still have to deal with the problem of air loss.
I've thought it would be interesting to try putting a rifled barrel on a ridiculously powerful gun.... say, if you were to make a plunger that moves 7 or 8 cubic inches of air at a high velocity. With that kind of power, the air loss would be beneficial, and the spin may be interesting.
It's possible that part of the problem with rifling is the low velocity of the projectile... It just doesn't have enough force to fly straight. In which case, a ridiculously high powered gun may actually benefit from this. Attach a rifled barrel to a cobra-powered gun? Just an idea.

Anyway, I kind of got off on my argument there, strayed away from the original point of the topic. But I figured I would put in my two cents. =)

EDIT: I'm sorry, the word I was looking for when I said "chamfered" was "countersunk"... although, it has essentially the same meaning, in this context.

Have a sizzlin' day,
AJ

[steadyon]

Thanks for the constructive criticism.

The whole reason I went this way is because this particular rifled barrel, is designed for a rediculously powerful nerf gun. one that dumps 24ci of air down the barrel, at a minimum firing pressure of 55Psi.

The loss of velocity in this case is negligible, as there is so much power to spare.
I weighed it all up, and my rifled barrel experiences no average drop in range over a smoothbore one.

The persuader is the gun in question. The benefit of the rifled barrel spin far outweighs any cons.

[AJ R]

Well, in that case, please share your results. I've been wanting someone to put a rifled barrel on a ridiculous gun. Because I'm sure at the velocity a gun like that could shoot a dart out at, rifling might help. One thing I will say, though, is that it may be a good idea to drill a few air release holes at the end of the barrel. When you're moving 24 cubic inches of air down a barrel, there's always the possibility of the air blowing the dart in to a spin... and I don't mean the good kind.
By the way, I have to ask... is this a spring gun, or is it a pump gun? Because if it's a spring gun, I'm going to have to ask how large the plunger system is.

Anyway, I would rifle a crazy powerful gun myself, if I had one.

Have a sizzlin' day,
AJ

[TantumBull]

I'm fairly certain rifling only really matters if the projectile's center of gravity isn't at the front.

[Doom]

I've said this before and I'll say it again: Show me the data that demonstrates rifling is more accurate. To make such a claim, you had to have done some testing.

FYI, I have demonstrated that "benefits" or rifling were not statistically significant before.

Rifling can improve stability of a projectile. However, Nerf darts are stable from their weight distribution (as TantumBull said, the center of gravity is near the nose). So rifling does not help unless the dart is so light as to have the center of gravity more than a certain distance from the nose.

I'm fairly certain that the hole in the back of darts doesn't do anything either. If anything, compression of the dart in the longitudinal direction (and resulting expansion in the radial direction) due to the pressure differential would drive it into the rifling more than that.

Edited by Doom, 20 February 2010 - 08:51 AM.

[JATDO]

So your making you darts to work similar to the Minie ball of the American Civil War, right?

[Talio]

This thread sucks.