Home Forums Hunting & Shooting Hunter's Campfire can a person 'hear' a bullet coming at him?

You can see them coming sometimes if they are moving slow enough, and if they are still supersonic all you hear is a semi-load “TICK” like sound when they go by.

If you want to hear it go to a high power range and get in the pit where the targets are, you can hear them when they come through and see where they hit the dirt if they miss the target.

My wife says I can't hear her talking most of the time.

How the hell I could hear a supersonic bullet before it hits me is beyond me.

Probably different situations, but the outcome is probably the same: not good.

For the guy lobbing bullets over my head from a long way off, he took a couple shots. After the first one and I knew what was happening and I was safe I paid attention. Could hear the sound get a little louder then a little weaker. Not much sound, a whisper not a shout. But in no case did the sound register in my brain until the bullet had passed. Subsonic, but if you check your ballistics program that a bullet doesn't slow nearly as quickly once it goes below transoic. So it's here and gone in an instant.

The barrel is full of hot expanding gases, no vacuum! What would push the projectile out if there was a vacuum?

Any you bought that?

It's true that there is - very briefly - a moment of sub-ambient pressure in the barrel after the expanding gasses leave. I would not describe it as a "near perfect vacuum" but for a millisecond or so, there can be a partial vacuum, simply because virtually all the gasses produced have rushed out. The air rushing back in would create a small sound wave - but that is most definitely not the source of the BANG.

I agree.

Don't forget that the gas in the barrel is still under pressure when it begins to cool. In the case of a center fire rifle may be several kpsi. I'm sure somebody somewhere has gauged it.

Ok. Cheated a bit and just Googled up pressure traces. Got this one and if you zoom in on the data the last line shows that at the 0.001222 second mark the bullet had travelled 30 inches, was going 3663 fps. And the barrel pressure was still 6564 psi. None of the charts Google produced showed pressure going below zero. Turns out the chart below came from Varmint Al's site.

I doubt that you will hear one coming at you. But you can hear it as it passes, especially if its still super sonic. Like other have said, this is common if you are working the pits at a match. You can hear the bullet hit the target too.

I have been shot at (towards) a bunch with .30-06 class rifles from several hundred yards. I assume the projectiles were still supersonic. What I would hear was an eerie loud sucking sound, a sonic crack, and then the muzzle report. I would assume that I would have heard nothing had I taken a hit. The muzzle report arrived noticeably after the first crack.

Well you would've heard it with your ears but your brain would be disrupted before it could process the signal from your ears.

Two points about that graph, nighthawk: One, those traces normally end at bullet exit with no data shown after that. Two, the graph is extrapolated a bit due to the fact that the sensing system may not be fast enough to record small variations - one of which would be the nearly instantaneous drop to less than ambient pressure after bullet exit before bouncing back to ambient.

Strangely enough, I am one of what must be a tiny handful of people who have experienced inbound full auto fire when bird watching

For more’n ten years I was part of a crew monitoring two endangered bird species on Camp Bullis Military Training Area right outside of San Antonio. The hardest part to get into was Area 9, the ranges and range fans behind ‘em, the ranges being usually in use, civilian or military.

After some years of a) always answering my radio and b) always being exactly where I was supposed to be, one time on the basis of necessity I was allowed access to the range fan while full auto fire was going on.

I was on the lee slope of a low ridge, behind the targets, the full-auto guys (dunno what weapons, had to be 7.62 tho as IIRC fifties were no longer allowed). The full auto guys were firing at old vehicles IIRC two or three hundred yards away on their side of that ridge.

Incoming fire?

A metal on metal “Plonk! Plonk! Plonk! Plonk! Plonk!”

Followed immediately by a “whoosh whoosh whoosh whoosh whoosh” of the inbound bullets.

And then a more distant “bang bang bang bang bang” from the gun.

IME

Delta P would be my swag. At powder ignition pressure rises quickly and begins to equalize with atmospheric pressure thru the path of least resistance; that being the barrel though corked by a bullet. As chamber pressure increases the bullet moves forward seeking pressure equilibrium. As this occurs available volume for expanding gases increases but not rapidly enough to prevent a large pressure delta forming between atmosphere and the now swollen "chamber". However, when the bullet exits the muzzle that situation changes dramatically. Suddenly our entire atmosphere is available to the hot expanding gases allowing a large pressure bubble to form. Now pressure equalization between these gases and ambient pressure occurs. And here comes the BOOM.

Think lightening vs thunder as gunshot vs blast. Lightening splits the atmosphere with its gigantic level of heat. Rapidly burning gunpowder splits the atmosphere with heated gases but not to the same level. But in each case the heat rapidly created disperses at an equally rapid rate forming the vacuum mentioned. Now we have negative pressure with regard to atmosphere where a nano second ago it was positive. Delta P again takes over as atmospheric pressure seeks equalization between itself and the negative pressure suddenly created and our atmosphere slams together in that void. Thunder/muzzle blast results. And that's my SWAG.

The government has nothing on me when it comes to lengthy explanations.

I've heard plenty of ricochets coming in, sub sonic and mostly tumbling.

That was the second coolest thing that happened to me on Bullis, the coolest was the the time I was sampling a transect across the LZ; a large open space, relatively flat.

There I was in my orange vest with pen, clipboard and binocs when this not-all-that-high C130 flew over and guys with parachutes start bailing out in quick succession, landing all around me.

I called Bullis Control on my radio thinking for sure I had screwed up and was in the wrong training area. They said I was OK, they didn’t think I would get in the way.

Rocky,

I picked that graph because it had numbers, there are a lot of others with extended tails that show no drop below zero. Now we don't know the conditions under which the charts were produced but of the plethora of charts Google produced you'd suspect one would show a negative bump if it was substantial. Like I said I took a shortcut.

And we do not know the response time of the pressure gauge. But having fooled around with the design with suitable and readily available op amps the response time can be very quick indeed. "Nearly instantaneous" - remember you're still dealing with a substantial volume of gas in a confined space. May appear nearly instantaneous in our time frame but it takes time to move a significant mass of gas.

But I don't know, that's far from conclusive. Would be interesting if someone would come up with data showing a dip below zero psi..

I knew I should've paid more attention in physics class.

Interesting thread.

I've heard bullets spinning through the air wilst hunting in Colorado a few times. First you hear that, then you hear the report from the firearm. Don't know how close they have wizz by in order to hear them.

I have definitely have heard them pass overhead.