Ballistics and how less power is more energy delivery.

[Rogerborg]

9 hours ago, EDcase said:

drop an equal projectile

 

You could drop a feather and it would hit the ground at the same time, but only if your firing range is in a perfect vacuum.  Be sure to double-mask so you can breathe.

[EDcase]

3 hours ago, Rogerborg said:

 

You could drop a feather and it would hit the ground at the same time, but only if your firing range is in a perfect vacuum.  Be sure to double-mask so you can breathe.

Yeah, I already know that (shocker)

I'm talking on Earth...

 

...and its funny that the same isn't true for airsoft BBs because of the magnus effect.

With the power of a sniper rifle its interesting that the bullet still drops at the same speed.

 

Edited November 4, 2021 by EDcase

[AirSniper]

Magnus effect has little to do with this. 

I am stating facts that THERMODYNAMICS and PHYSICS as rule here and the very same method that is used to chrono your airsoft RIF is the same method used in archery, airguns and real steel.

 

I have provided enough examples of this reality but please live in denial all you like. Magnus effect or not, all bullets have spin even airgun pellets. So by that measure, you can negate that as a factor as it is common and just for simplicity sake. Axial or Pitch have the same effect on helping the projectile stay on target, what IT WON'T STOP is GRAVITY pulling on it OVER TIME which equals RANGE.

As for the feather hammer experiment, yes that is true but a bullet has a hot gas that is providing that thrust

 

[AirSniper]

SO... a 0.2g BB is a 3.08 grain BB

and a 0.4g BB is a 6.17 grain BB

Assuming that there is a fixed 0.8 Joule limit on the power of the RIF in this example, you will get the following results for the muzzle velocity.

From that you can calculate the range over time and the known act of gravity and air resistance and so on, get an accurate range and flight path.

On this Airgun site, the data about the RIF that a comment in a thread was referring to, this again, shows that the very same ballistics calculators work for airsoft as they will for live round shooters.

I have shown that to go faster you need a lighter BB, this speed affect the flight time because its is also a measure of distance over time, per second, so if you have a BB with a 4 second flight time before it drops out, its chrono was 200 fps, then you know its travelled 800 feet. or 243 meters.

If you could throw a stone through a chrono and time it, you would be able to work out the amount of KE you put in to that projectile. So I don't see why people are finding it hard to believe that the same math for ballistics applies no matter the scale or where you are. 

 

[Rogerborg]

5 hours ago, AirSniper said:

please live in denial all you like

 

Have you considered the possibility that you've burst into a pub and are shouting "I LIKE BEER! WHY DO YOU ALL HATE BEER?" at a rather bemused clientele?

[Adolf Hamster]

7 hours ago, AirSniper said:

what IT WON'T STOP is GRAVITY pulling on it OVER TIME which equals RANGE.

 

except that is very very literally what the magnus effect does to an airsoft bb.....

[Rogerborg]

10 minutes ago, Adolf Hamster said:

except that is very very literally what the magnus effect does to an airsoft bb.....

 

Granted, it doesn't stop gravity pulling down, and the force to counter it has to be powered from the energy in the BB.

 

What I'm curious about is whether it's all coming from the angular velocity (shouldn't reduce range) or is also bleeding it from the linear (will reduce range).

 

(I assume here that we've got perfect backspin and site-limit muzzle energy for whatever mass of BB we're shooting).

[EDcase]

8 hours ago, AirSniper said:

Magnus effect has little to do with this. 
Magnus effect or not, all bullets have spin even airgun pellets. So by that measure, you can negate that as a factor as it is common and just for simplicity sake....

...what IT WON'T STOP is GRAVITY pulling on it OVER TIME which equals RANGE....

These statements shows you're clearly missing some crucial physics knowledge to understand the difference between BBs with Magnus effect versus an axial spinning projectile.

 

Edited November 5, 2021 by EDcase

[Adolf Hamster]

 

9 minutes ago, Rogerborg said:

What I'm curious about is whether it's all coming from the angular velocity (shouldn't reduce range) or is also bleeding it from the linear (will reduce range).

 

damn you, making me have to go do math......

 

so for 0.5 seconds of flight time, with a muzzle energy of 1j and hop set for ~20cm of rise above muzzle:

a 0.2g bb will lose 0.002406j due to gravitational potential energy and 0.9j due to drag forces

a 0.5g bb will lose 0.006015j due to gravitational potential energy and 0.58j due to drag force

 

granted that's a very oversimplified calculation based on simply the flight time (ie not counting energy that would accelerate the bb upwards to get that 20cm of rise), but then the drag model is pretty over-simplified as well.

 

however the point is it's a negligible amount compared to the primary force which is the conventional drag.

[Rogerborg]

Officer work, thanks.

 

With the understanding that it doesn't really matter, I wonder how much rotational energy we have to donate before it has to come from the linear.

 

Moment of inertia of a sphere, I, is 2/5 mR²

 

Rotation energy is 1/2Iw², where I is as above, and w is the angular velocity (how fast it's spinning, radians per second if we're doing SI rather than fathoms-per-demihectare).

 

I make that 1/5 mR²w²

 

We know m (e.g. 0.004kg), R (e.g. 0.002975m), now we just need to paint a BB with a battenburg patten and film it with a high-speed camera to find out w.

 

Granted we're down at 0.0000000070805 w² for a 0.4g BB, so we're not talking big numbers.

 

 

[Tackle]

29 minutes ago, Rogerborg said:

Officer work, thanks.

 

With the understanding that it doesn't really matter, I wonder how much rotational energy we have to donate before it has to come from the linear.

 

Moment of inertia of a sphere, I, is 2/5 mR²

 

Rotation energy is 1/2Iw², where I is as above, and w is the angular velocity (how fast it's spinning, radians per second if we're doing SI rather than fathoms-per-demihectare).

 

I make that 1/5 mR²w²

 

We know m (e.g. 0.004kg), R (e.g. 0.002975m), now we just need to paint a BB with a battenburg patten and film it with a high-speed camera to find out w.

 

Granted we're down at 0.0000000070805 w² for a 0.4g BB, so we're not talking big numbers.

 

 

 

[Adolf Hamster]

30 minutes ago, Rogerborg said:

Officer work, thanks.

 

With the understanding that it doesn't really matter, I wonder how much rotational energy we have to donate before it has to come from the linear.

 

Moment of inertia of a sphere, I, is 2/5 mR²

 

Rotation energy is 1/2Iw², where I is as above, and w is the angular velocity (how fast it's spinning, radians per second if we're doing SI rather than fathoms-per-demihectare).

 

I make that 1/5 mR²w²

 

We know m (e.g. 0.004kg), R (e.g. 0.002975m), now we just need to paint a BB with a battenburg patten and film it with a high-speed camera to find out w.

 

Granted we're down at 0.0000000070805 w² for a 0.4g BB, so we're not talking big numbers.

 

 

 

yes the angular velocity is a bit of an unknown.

 

in the spreadsheet i made a while back i ended up having to go with a macro and goal seek to just brute force it, hence the whole "20cm of rise" caveat as there needed to be a fixed goal to look for. although tbh a few corners were cut, eg the magnus force was simplified to the force for a cylinder of equivalent cross section rather than doing it properly and splitting it up into increments, or the very oversimplified drag model that treated air as an incompressible fluid. but then i was doing it because i was bored/curious so an approximation was good enough

 

for the aforementioned 1j of muzzle energy and 20cm of rise criteria it would come out as:

63.67 rad/s for 0.2g

79.54 rad/s for 0.25g

97.03 rad/s for 0.3g

133.46 rad/s for 0.4g

173.293 rad/s for 0.5g

 

it's part of the reason why as mentioned, heavier=better doesn't always hold true practically, when the losses in the hop to acheive sufficient spin drop the energy enough to the point where a lighter bb from the same gun would go further.

 

fun anecdote- it's possible to have 2 "sweet spots" for hop, first when you've just enough pressure to get the spin, then turning the hop on further results in the expected overhop, but go too far and the energy will drop to the point where it'll meet a second spot, with a much higher spin but lower energy.

 

although more usually by the time you get to that point the gun just jams.

 

3 minutes ago, Tackle said:

 

 

[EDcase]

The answer is out there...

 

....waaaaaay out there 😆

[Rogerborg]

32 minutes ago, Adolf Hamster said:

133.46 rad/s for 0.4g

 

I make that 0.0001261148327138J of rotational kinetic energy, or a lot less than that required to hold it up, so it's got to be leeching that (small) amount from the linear.  Insignificant compared to the drag, I was just curious, unlike some peasants in here.  

 

[EDcase]

I'm not a peasant

I'm a serf 😋

 

Wow, this thread has definitively come off the rails and into a ravine.

[Adolf Hamster]

10 minutes ago, Rogerborg said:

I make that 0.0001261148327138J of rotational kinetic energy, or a lot less than that required to hold it up, so it's got to be leeching that (small) amount from the linear.  Insignificant compared to the drag.

 

yeah, can be fun to delve into this sort of thing, tbh i'm surprised it's that small myself figured it'd be a more major component.

[Tackle]

1 hour ago, EDcase said:

😋 this thread has definitively come off the rails and into a ravine.

About time I reckon 🤔, its got boring as f#ck😴

[Lozart]

13 hours ago, AirSniper said:

Magnus effect or not, all bullets have spin even airgun pellets. So by that measure, you can negate that as a factor as it is common 

 

Except you can't, because the Magnus effect in the case of airsoft BB's provides lift. It also produces increased turbulence in the BB's wake which contributes to drag which affects the terminal energy.

 

Axial spin in rifled barrels increases range by the conservation of angular momentum which is a whole different kettle of ballistic fish.

[Adolf Hamster]

3 hours ago, Tackle said:

About time I reckon 🤔, its got boring as f#ck😴

 

What do you mean? From my perspective it just got interesting?

[Rogerborg]

12 minutes ago, Adolf Hamster said:

What do you mean? From my perspective it just got interesting?

 

Really?  Nobody's been offered out IRL yet.  

[Shamal]

6 hours ago, Tackle said:

 

Haha 😅

I  point de small end towards baddies,pull on da sticky down fing and see white balls come out da small end. Job done,I happy.🙂

 

Regards 

[AirSniper]

Russians go do something stupid

 

Excellent example of a high velocity impact by a tiny projectile in a vacuum travelling at speeds I understand are 20 times the speed of a bullet...  Fast Forward to 9:15.

 

[Guest]

“Never argue with a fool, onlookers may not be able to tell the difference.”

 

“Never argue with an idiot. They will drag you down to their level and beat you with experience.”

― Mark Twain

[Tommikka]

11 hours ago, AirSniper said:

Russians go do something stupid

 

Excellent example of a high velocity impact by a tiny projectile in a vacuum travelling at speeds I understand are 20 times the speed of a bullet...  Fast Forward to 9:15.

 

Correction - Russia do a thing knowing the risk & not caring

[AirSniper]

Point again that Ballistics works in space... Shows that even in LEO that the pull of gravity can affect an object unless it is travleing with enough energy to carry it in to space.

Again, some of these "Projectiles" are the size and weight of flecks of paint.

In space a fleck of paint travelling at the speeds of a bullet in space carries enough momentum that if it hits something, can crack that thing, chip it or in some cases, pass straight through the hull of the ISS. 

Again, I draw attention to the fact that ballistics works any where and the denial by some that the same calculations for airsoft are the very same calculations used in daily science for calculating KE, even in air gun and live round shooting, archery and so on. 

It seems to be a lost fact on people.