SpudFiles

I think if you want a professional copy then vacuum forming is the way to go.

I was thinking blow moulding,but vacuum would also work well.Milk jug HDPE seems to me a perfect material in thickness.Although I would not add the rifling to the ones I make as it seems nothing more then an oh ah factor.

jackssmirkingrevenge wrote:You could even try a ring of masking tape around the paintball, I have my doubts as to how effective the "air rifling" is as opposed to the fact that a hollow tail adds draw stabilisation.

I tried this out. I added a ring of paper(normal A4 printer paper>one revolution) (of 1.5- 2cm in length) behind the paintball. It didn't have the desired effect; it was actually less accurate(all over the place) compared to a normal paintball. I did make a movie(attached a camera to my paintball marker) but I don't think its worth posting it, bc the result was nowhere nice..

rna_duelers wrote:I was thinking blow moulding,but vacuum would also work well.Milk jug HDPE seems to me a perfect material in thickness.Although I would not add the rifling to the ones I make as it seems nothing more then an oh ah factor.

You need the rifling for sure!!! Do you really think they only added it to make it look good? You how much that rifling increase the price with. As I said above, non rifled first strike like shots don't have the desired effect.

We need to see them in flight with a highspeed camera before we accept this air rifling they claim.

frankrede wrote:We need to see them in flight with a highspeed camera before we accept this air rifling they claim.

How come you don't believe that effect? The drag coefficient of a sphere is about 1.2, that of a bullet shaped object is about 0.3, this is 4 times less! You also have to realize that just like a pellet round the first strike already starts to rotate inside the barrel. Because of its hollow back the pressure from the air makes the rifling push against the sides of the barrel while it is travelling allong the barrel at the same time.

Antonio wrote:The drag coefficient of a sphere is about 1.2

I don't know where you got that number from, because all the tests I know of show spheres to have a Cd that is between 0.3 and 0.5 depending on surface texture and roughness - and specific velocity of course, but I'm talking at relatively low Mach numbers here. Certainly within paintball speeds.

Even a flat plate, which is about as ballistically inefficient as it's possible to be doesn't quite reach a Cd of 1.2 at low airspeed velocities.

The closest ballistic shape to the First Strike is the GL ballistic model, which at paintballing velocities has a Cd around ~0.3, depending on exact velocity.

So you're close on the 1st strike's Cd, but highly off on the Cd of the sphere.

Because of its hollow back the pressure from the air makes the rifling push against the sides of the barrel while it is travelling allong the barrel at the same time.

The fact it's pushing against the walls is pretty moot, because it hasn't the hardness to grip into the walls, and if the walls are even vaguely smooth in the first place, the effect in the barrel is going to be very limited.