Putting a debate to bed.

[Unrustle_Thine_Jimmies]

FPS Does have an effect on range to a certain extent,something around 380 but past that the wind resistance just flings the BB around unstably.

I remember seeing this claim on an old ASSF thread which I will attempt to dig up..

 

[ScoobySnacks]

OK, massively over simplified. The answer is, what you state as "basic physics" isn't necessarily correct.

If you are talking an ideal situation, then yes, a similar weight BB starting out at a greater MV will travel further than its slower brother. Also, a heavier BB started out with a similar MV will travel further than its lighter brother (given that the backspin caused by the hop is sufficient to create the lift required to overcome gravity)

There are all sorts of aerodynamic equations involved with this stuff, it's not "basic physics" by any means.

The rate of backspin (rpm) required to provide the lift needed to overcome gravity is much higher for a heavier BB. Lift comes at a cost (called lift drag) so a heavier BB, which requires far more lift than a lighter one, will actually experience more drag and therefore MIGHT (it's a trade off type thing which requires a fair amount of maths to work out the best compromise) actually slow down faster!

Also remember that applying more backspin requires a much tighter hop (and therefore a much higher initial energy input) to achieve. This means that your gun has to work a lot harder to accelerate that BB up to the same energy. This means that your gun will almost certainly not achieve the same energy level with a higher BB weight, unless it's specifically tuned to do so.

So, in answer to your poll, the answer is "it depends".

If you want me to go through the lift/drag equations I can, though it would mean dragging up some old uni work.

 

[Ian_Gere]

Hey Scoob, you must be the person who can tell us exactly why the lift effect of backspin produces that hop up as the BB slows down...?

 

[sp00n]

Hey Scoob, you must be the person who can tell us exactly why the lift effect of backspin produces that hop up as the BB slows down...?

the back spin produces a area of high pressure, behind and above the bb, as the bb slows, the area of high pressure moves closer to the bb, increasing air resistance further, and "hopping"

 

[Airsoft-Ed]

If people know all this stuff, then why isn't it documented?! There needs to be genuine studies done on this sort of thing.

 

[sp00n]

if i had access to solid works (CAD package) i could simulate it

edit :- i am sooo far out of practice with cad packages, i dont think i could any more

 

[sp00n]

this should explane a lot .... but its quite big worded >>> http://en.wikipedia.org/wiki/Magnus_effect

however please do note in the above example, it uses a base ball ... good for basics, but not for airsofters, as our bbs are usually a lot lighter, hence the bb slowing "hop" effect

edit:- i just want to add, the FPS may slow, however the rotations/sec will still be pretty high, which is why it hops. this effect also explanes why your bb can go skywards with too much hop (increased rotation/sec, with the same FPS etc)

 

[Ian_Gere]

Ed it is documented - it's the science of ballistics. It's just that A. it's really complex so for some people the pull of the tv, x-box, their "friend's" most recent inanity on fb, in fact anything that requires less concentration, will always trump learning something, thus people have to precede such discussions with "if you find this tedious you're a penis" and there are only so many times that such people can stand acknowledging to themselves that their intelligence really does separate them from the mass of humanity, hence bringing up complex science in connection with hobbies is rarely done, and B. for anyone who does understand ballistics in the kind of depths the details of our discussion have reached, the prospect of having to teach random forum members enough physics to take them from some unknown degree of understanding to post grad applications has got to be a bit daunting.

 

[ScoobySnacks]

And C, research is expensive! That's why areas that can make money (pharmaceuticals, electronics etc.) get FAR more research done than areas that aren't as lucrative.

 

[ScoobySnacks]

And as for the "hop up" at the end of flight, I reckon spoon has it about right. The velocity decreases, but the rate of spin doesn't (at least not as much) As this happens, (you can work it out with vectors, a fast moving BB has more "form drag" which shifts the "centre of pressure" further forward. As the BB slows this shifts the vector to a more vertical direction) the "centre of pressure" (the place on the BB where the lift can be said to act) moves closer to the "centre of gravity" (the point on the BB where the mass can be modelled as acting) and hence there is more lift vector acting in the "up" direction, hence the ball may climb somewhat.

 

[Ian_Gere]

Yeah, my limited understanding told me it must have something to do with the angle at which the drag affects the BB and what shape of 'wing' the vortices around the BB make. It's sort of the same as why counterintuitively a pick up truck with the tailgate up is more fuel efficient than with it down or off, b/c the vortex trapped in the back by the tailgate has a smoother profile than if the drag just sucks at the back of the cab...