Page 2 of 2 FirstFirst 12
Results 16 to 29 of 29

Thread: A silenced 9 mm appears to be louder than a crossbow

  1. #16
    Zombie Hunter ZombieSurvivor's Avatar
    Join Date
    Sep 2017
    Location
    End of The Rainbow
    Posts
    411
    Rep Power
    1
    Quote Originally Posted by Damocles View Post
    You can hear two sounds when the bullet passes. The first high pitch is the (supersonic) bullet, sounding like a whip, the second (delayed) is the muzzle gas-expansion.

    That "whip" sound, is what gets suppressed with sub sonic ammunition.

    An AK47 has a muzzle velocity of 2,350 ft/s whereas the speed of sound is 1,125 ft/s. So its more than twice as fast. (but will slow down of course)

    If you suppress the muzzle, the bullet can be still heard loudly, but not the direction where is came from. Its way harder to pinpoint the position of the shooter from the muzzle sound.
    You know your stuff, nice. I would add though, a bullet can be fired slower than the speed of sound and still produce a sonic boom i guess you call it. This is caused by the compression of the air infront of the bullet and the air being compressed having to flow around the bullet can be faster than sound thus causing and sonic boom. gotta love science.

    Note: I'm probably explaining this incorrectly lol, i do not feel like looking this up in detail.
    Last edited by ZombieSurvivor; 4 Weeks Ago at 05:33 PM.

  2. #17
    Inventor
    Join Date
    Jul 2017
    Posts
    801
    Rep Power
    1
    Quote Originally Posted by Fox View Post
    [url]
    <snip>
    But I'm also thinking about how long does the bullet stay past the barrier... cuz most bullets are only set for a bit past the sound barrier.
    Happened to notice on the wikipedia page for 7.62x51 that one of the loads stayed supersonic out past 1100 yards. Most reloading tables don't go past ~5-600 yards for rifles, so can be hard to find where a given round drops down.

    On the second bit... hmm. History wise that's pretty true. Black powder burns faster than modern smokeless does, so in a sense, chamber pressure was a bigger deal. Also non-cladded bullets (exposed lead) limited speeds. Much past ~1350 fps and there'd be a lot of lead left coating the bore.

    More modern stuff it's mainly the 'pistol' rounds that stay under say ~1400 fps. While I can't think of a modern rifle round that would be under a couple thousand feet per second (at the muzzle) off the top of my head, one bunch that might well be there would be some of the newer 'large mammal brush gun' rounds. Large caliber, very heavy bullet rounds designed for use hunting bear or moose. Basically modern day cousins of the classic Nitro Express african rounds.

    Quote Originally Posted by Damocles View Post
    <snip>
    If you suppress the muzzle, the bullet can be still heard loudly, but not the direction where is came from. Its way harder to pinpoint the position of the shooter from the muzzle sound.
    Absolutely. And one of the main reasons 'snipers' use suppressors even with full power, supersonic loads. Other being that cans greatly reduce the muzzle flash (and dirt plume from the gases).

    On the supersonic 'crack'. I can't quote the physics/math but there's a definate correlation between how loud the crack sound is and the speed of the bullet. There's a noticible difference between a .22 LR moving at ~1300 fps vs. a 5.56x45 (which is also a .22 caliber bullet) moving at over 3000 fps.

  3. #18
    Zombie Hunter ZombieSurvivor's Avatar
    Join Date
    Sep 2017
    Location
    End of The Rainbow
    Posts
    411
    Rep Power
    1
    Quote Originally Posted by FileMachete View Post
    <snip>
    On the supersonic 'crack'. I can't quote the physics/math but there's a definate correlation between how loud the crack sound is and the speed of the bullet. There's a noticible difference between a .22 LR moving at ~1300 fps vs. a 5.56x45 (which is also a .22 caliber bullet) moving at over 3000 fps.
    The first video i posted goes in depth the science behind it if you are curious to know why and how this happens. I suck at explaining things in text, talking ov video on the other hand very easy, best just to watch the vid lol

  4. #19
    Inventor
    Join Date
    Jul 2017
    Posts
    801
    Rep Power
    1
    Quote Originally Posted by ZombieSurvivor View Post
    The first video i posted goes in depth the science behind it if you are curious to know why and how this happens. I suck at explaining things in text, talking ov video on the other hand very easy, best just to watch the vid lol
    hmm, I watched them both... First one went into how the angle of the wave front could be used to calaculate the Mach number, which is very cool, but I don't recall them talking about the energy levels or how they related to the sound pressure?

    I mean, no question it makes sense that the larger and faster an object is that breaks the sound barrier, the louder the sonic boom will be, I just can't point a finger at an equation that would show the .22 LR's boom as X dB and the 5.56 as x% more.

  5. #20
    Zombie Hunter ZombieSurvivor's Avatar
    Join Date
    Sep 2017
    Location
    End of The Rainbow
    Posts
    411
    Rep Power
    1
    Quote Originally Posted by FileMachete View Post
    I mean, no question it makes sense that the larger and faster an object is that breaks the sound barrier, the louder the sonic boom will be, I just can't point a finger at an equation that would show the .22 LR's boom as X dB and the 5.56 as x% more.
    Oh my bad I misunderstood your statement, I re-read it. Yeah nevermind those videos do not address any of that. Now I am curious and I'll look in to it because now I want to know. If I find an answer I'll post an update.

    EDIT #1: Interesting article, does not answer what we are talking about but interesting none the less. http://firearmsid.com/Feature%20Arti...ofbullets2.htm
    Last edited by ZombieSurvivor; 4 Weeks Ago at 07:45 PM.

  6. #21
    Inventor
    Join Date
    Jul 2017
    Posts
    801
    Rep Power
    1
    Quote Originally Posted by ZombieSurvivor View Post
    Oh my bad I misunderstood your statement, I re-read it. Yeah nevermind those videos do not address any of that. Now I am curious and I'll look in to it because now I want to know. If I find an answer I'll post an update.
    No worries From some skimming I think it's going to wind up being a fairly deep fluid dynamics problem, without a simple equation.

    But a maybe(?) fair short version is that the main contributer to the overall energy is the frontal area, _not_ the speed. So my perceptions my be totally wrong on the diff between a .22 & a 5.56...
    <won't be the first time... -I- thought the dress, did indeed, make her butt look big... >

  7. #22
    Leader Fox's Avatar
    Join Date
    Oct 2013
    Location
    Under the snow
    Posts
    5,681
    Rep Power
    1
    Quote Originally Posted by FileMachete View Post
    hmm, I watched them both... First one went into how the angle of the wave front could be used to calaculate the Mach number, which is very cool, but I don't recall them talking about the energy levels or how they related to the sound pressure?

    I mean, no question it makes sense that the larger and faster an object is that breaks the sound barrier, the louder the sonic boom will be, I just can't point a finger at an equation that would show the .22 LR's boom as X dB and the 5.56 as x% more.
    I've seen those 2 videos in the past as well and like you said, it didn't answer any sound questions I had. But ya, that's exactly what I'm wondering now. If a jet makes a loud enough boom to pop windows and stuff and a bullet cannot even at 1cm away... what exactly is the equation for sound dB? I assume weight doesn't matter and length of the object doesn't matter either, my only guess would be the size of the tip causing air redirection. So I wonder if the tip of a bullet makes a big difference when it comes to sound? Cuz there's flat tips (which is the ammo I usually create for my .308), and there's also pointed tips (usually copper coated). I've also seen experimental bullets fly sideways (due to bad aerodynamics), I imagine the sound for that would be different too. Personally, when I fire them both off, they sound the same to me, but maybe at a distance, there's a difference? Anyone dumb enough to stand downrange... for science? lol
    Last edited by Fox; 4 Weeks Ago at 08:21 PM.

  8. #23
    Refugee
    Join Date
    Apr 2019
    Posts
    3
    Rep Power
    0
    I'd likely ask the question: Were you in stealth at the time? Because a silencer is not a really strong gaurantee.
    I've been a strong crossbow user in the past and I've had zero issues killing sleepers so long as the bolt connects to the head.
    Also, I've had better luck with the vanilla wooden bow than I've had with the crossbow.

    Now, shots hitting any other portion of the body, or walls, glass, etc etc is another matter. Corners of things can also block shots even if
    you think you have a clear aim. I can count on many hands the number of times I thought I got a head shot, only to find the
    arrow OR bolt is stuck in an invisible hit box of a countertop or a dresser. It's very frustrating.

    Also, if you have loud teammates they tend to ruin the ninja's A-Game without any doubt. But, that's an interpersonal issue, not really a gameplay one.

  9. #24
    Refugee
    Join Date
    Mar 2016
    Posts
    4
    Rep Power
    0
    Honestly with silencer/suppressors I don't care about reality, I would prefer to be able to kill 10 zeds in 5 seconds without make any sound. I love playing with guns in Far Cry for example and would love to be able to do the same here. The problem with guns now is, if you use them you can get overrun quickly.
    I remember some times, when I played 7d2d and just head shot every sleeper with a crossbow and I was fine. I would really love to be able (in mid or even only in late game) to kill sleepers with the 9mm and a suppressor with out being noticed.

  10. #25
    Hunter jdm311's Avatar
    Join Date
    Jun 2017
    Location
    Shop smart, shop S-Mart
    Posts
    123
    Rep Power
    0
    With advanced muffled connectors on each piece of armor and full stealth perks (hide in shadows), I've be able to use the silenced pistol without waking any z's, even when a few feet from to them. I think the sound meter read low 30s, iirc. The silenced marksman's rifle is another story. Much better for taking out the stronger rads, but easier to wake when close to another. I generally try to shoot far from another z when using that one. The sound meter registered mid 40s, iirc.

  11. #26
    Inventor
    Join Date
    Jul 2017
    Posts
    801
    Rep Power
    1
    Fox, see ZombieSurvivors link in his Edit. There are sound files of bullets passing by downrange

    They triggered a memory of a training course I went through in the military; live fire M60s (7.62) shooting over our heads as we navigated an obstacle course. At night, in the rain, of course... At the beginning of the course there was a ~15 foot high embankment that led up to the course with all the 'junk'; culvert tubes, razor-wire, pits, etc. We were all stacked up at the base of the wall, then the trainers started up the sirens, boomers, M60s, etc., then the "GO!!". But I remember hearing the bullets zinging by overhead and thinking, "oh ♥♥♥♥! those bastards weren't kidding, this -is- live-fire!". Once you were up onto the course itself the bullet sounds weren't as easy to identify, due to all the other sounds, and the muzzle blasts of the M60s.
    And I recall using a snow shovel to clean up all the brass inside the M60 towers. Thousands and thousands of rounds fired. No idea if they still do this now a days, been a few decades, heh

    nodOn, I agree with you actually. One of the reasons I keep hoping for a .45 ACP pistol to be added. Since the 'normal' .45 ACP round is well under ~1100 fps there isn't a supersonic crack to help wake the zeds.

    Though it shouldn't be too hard to make a modlet to add in sub-sonic rounds for both the 9mm & 7.62 rounds.
    If the modlet kept to 'rl' then both rounds would wind up being about the same in 'power'. Which wouldn't be a big deal with the 'sneak shot' bonus, but would sure be felt by the Marksman rifle in a non-stealth fight; so we'd get good quick at swapping out ammo types

  12. #27
    Refugee
    Join Date
    Apr 2019
    Posts
    3
    Rep Power
    0
    Also consider this: Sneaking and trying to be a ninja without an actual ninja build, is not going to yield the results some look for. If you enter a house on day one with your newbie bow while in stealth there could be issues. With proper perks and gear, you'll see a dramatic difference.

  13. #28
    Reconstructionist
    Join Date
    Dec 2014
    Posts
    520
    Rep Power
    0
    https://www.youtube.com/watch?v=z17UQUYzPhQ&t=1204s at 15:17 is probably one of the funniest videos I've ever seen about suppressed firearms. It's a 300 blackout bolt action with a fancy suppressor. The loudest things you hear when he fires is the action/firing pin and then the distant sound of the bullet impact. Even with subsonic ammunition and a good suppressor you'll get some bang if you're using a firearm that uses exhaust gases to cycle the weapon.

  14. #29
    Refugee
    Join Date
    Jul 2018
    Posts
    29
    Rep Power
    0
    Quote Originally Posted by Fox View Post
    https://www.youtube.com/watch?v=ZpCu4bEUuQM


    I don't know... maybe I'm wrong... but it's so hard to tell if the sound demonstrated in the video is from the gunpowder explosion or if it's just the bullet whizzing by. Too bad it wasn't recorded in like 2000fps or something with an oscilloscope to prove 2 separate sounds.

    Thinking about the whip from Raiders of the Lost Ark... while not too ear piercingly loud, it's still impressive for a tiny piece of leather. But I'm also thinking about how long does the bullet stay past the barrier... cuz most bullets are only set for a bit past the sound barrier.
    Stand down range, about a half a mile away should do it, at a rifle being fired towards your direction. You hear are very loud crack and followed moments later by the gun being fired, the faster the round goes, the louder the little sonic boom. It almost sounded like some firing a .22 rifle next to you.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •