An odd question just occurred to me...

[maximus otter]

Can a typical rifle bullet be overtaken by the sound of its own discharge?

 

My pet .260 load launches a 139 gr. Lapua Scenar (G7 BC .290) at 2,758 fps, SD 5.1

 

It goes subsonic at about 1,250 yards.

 

Will there ever be a point - inside its theoretical maximum range of about 3 miles - where the sound of its firing will arrive before the bullet? My guess would be no, but maths isn't my strong suit, to put it mildly...

 

maximus otter

[JSC]

Interesting question...

 

Using the JBM calculator, your bullet takes about 7.2 secs to get to 2700yds and by then the sound from the rifle should have caught up with it:

Speed of sound is 375 yds/sec

(2700/375=7.2)

 

So, standing at 2800yds you should hear the gunshot before the bullet knocks the apple off your head, which might make you jump, so thinking about it best not try that particular trick shot...

[Gandy]

Interesting question...

 

Using the JBM calculator, your bullet takes about 7.2 secs to get to 2700yds and by then the sound from the rifle should have caught up with it:

Speed of sound is 375 yds/sec

(2700/375=7.2)

 

So, standing at 2800yds you should hear the gunshot before the bullet knocks the apple off your head, which might make you jump, so thinking about it best not try that particular trick shot...

 

Do you need to account for the diminishment of noise over distance i.e. would your hear such a noise that far away in any case?

[maximus otter]

 

Do you need to account for the diminishment of noise over distance i.e. would your hear such a noise that far away in any case?

 

Hearing the noise isn't the issue. The issue is whether the Mach 2.5 (and decelerating) bullet is overtaken by the Mach 1 (constant velocity) sound wave.

 

maximus otter

[Biathlonjimmy]

 

Hearing the noise isn't the issue. The issue is whether the Mach 2.5 (and decelerating) bullet is overtaken by the Mach 1 (constant velocity) sound wave.

 

maximus otter

 

Surly this happens when a bullet goes from super through trans to subsonic. This is why bullets can be awful once they have gone through this stage i.e. TR bullets at 1000yrds.

[gbal]

Hero to Zeno, in 10 seconds.....

 

Torty the tortoise (or 22short) challenged Achilles ,supreme Greek athlete (or 220Swift) to a race,claiming he'd win if Achilles gave him 10m start...

 

"No way" laughed Achilles.." How you figure that Torty?"

 

"Well" replied Torty "How long will it take you to cover the 10 metres?"......"Not long"..

 

"OK but Ill have moved on a bit meanwhile,agreed?"....."Yes,a bit"

 

"And how long willit take you to cover that bit?"......."Hardly any time at all"

 

"OK,but I'll still have moved on a little bit?" ......"Yes,of course"

 

"So I'll always be ahead,even if it's just a tiny tiny bit?" ..... ("Err...yes"

 

"So I'll get to the finish line a teeny ,teeny weeny bit in front and win"......."Well,yeah.. If you explain it like that...you do!"

 

Answers, with Strelok print out please.

 

gbal

[bradders]

A 139 Scenar will take 20.5 secs to travel 5000 yds with a MV of 2760, terminal velocity around 500fps

 

Sound at 1125 fps, or yards per second (375.11) will cover the same distance in 13.3 secs

You'll need 1029 MOA elevation though!!!

 

Working backwards, it will take the bullet 7.31 secs to travel 2750 yds, and sound will travel that in 7.33 secs

 

 

What is more important is that our nearest neighbouring Solar System is 2.5 million light years away, so any Alien there watching Earth through a telescope will just see a lump of ice......and this is why we've never been visited

[Gandy]

What is more important is that our nearest neighbouring Solar System is 2.5 million light years away, so any Alien there watching Earth through a telescope will just see a lump of ice......and this is why we've never been visited

 

You caught what I was saying then...

[cooter]

The sound will overtake the bullet.

There are some US 2 mile shooters on this vid and they record the sound on the target cam before the impact.

 

 

[gunner]

On October 18, 2017 at 3:54 PM, bradders said:

A 139 Scenar will take 20.5 secs to travel 5000 yds with a MV of 2760, terminal velocity around 500fps

 

Sound at 1125 fps, or yards per second (375.11) will cover the same distance in 13.3 secs

You'll need 1029 MOA elevation though!!!

 

Working backwards, it will take the bullet 7.31 secs to travel 2750 yds, and sound will travel that in 7.33 secs

 

 

What is more important is that our nearest neighbouring Solar System is 2.5 million light years away, so any Alien there watching Earth through a telescope will just see a lump of ice......and this is why we've never been visited

The late Gordon Cooper ( astronaut ) would disagree . His one of many interviews on Utube is still there for all to see . Why would a NASA astronaut tell porkies ? This is just 1 of many clips / interviews iv been looking at . It facinates me . There is alot of fake rubbish . Edger Mitchell ( NASA astronaut ) also tell his thoughts on the subject and again on U tube still . Gary heseltyne speaks about the Rendalsham incident in facinating detail and so do some of the witnesses who were there . Theres tons of information out there if you look and have time . Of topic sorry - atb

[Dalua]

Isn't the bullet actually responsible itself for a component of the of the sound until it goes subsonic?

If so, does that mean that the last gasp of its sonic crack will be audible before the arrival of the bullet at any point downrange after the bullets drops to below the speed of sound?

[VarmLR]

18 hours ago, Dalua said:

Isn't the bullet actually responsible itself for a component of the of the sound until it goes subsonic?

If so, does that mean that the last gasp of its sonic crack will be audible before the arrival of the bullet at any point downrange after the bullets drops to below the speed of sound?

That's what I was thinking.  If there is a strong headwind on the bullet and you were at a target 2.5Km distant, I'm not sure that with some cals you would even hear the muzzle blast but you should hear the sonic crack as it's a lot closer.