Question on the 5.56x45/.223 and the 7.62x39.

Question on the 5.56x45/.223 and the 7.62x39.

This is a discussion on Question on the 5.56x45/.223 and the 7.62x39. within the Defensive Ammunition & Ballistics forums, part of the Defensive Carry Discussions category; Assuming you have an AR-15 and an AK-47 with a 16" barrel or an 14.5" barrel for the AR-15(M4) with no muzzle brakes, which is ...

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Thread: Question on the 5.56x45/.223 and the 7.62x39.

  1. #1
    New Member Array LoneWolf69's Avatar
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    Question on the 5.56x45/.223 and the 7.62x39.

    Assuming you have an AR-15 and an AK-47 with a 16" barrel or an 14.5" barrel for the AR-15(M4) with no muzzle brakes, which is louder? The 5.56x45 or the 7.62x39?


  2. #2
    Distinguished Member Array Gunnutty's Avatar
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    7.62 x 39 is louder. My AK is definitely louder then my AR.

    Edit; just reread the barrel length difference in your question. My Ak and AR are both 16 inchers.
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    Distinguished Member Array BlueNinjaGo's Avatar
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    I don't own an AR yet, but I was firing my Ak next to a guy who was firing his AR (he was using .223 rounds) and my AK was louder for sure. (I compared while my girlfriend was firing btw.) Can't speak for the barrel lengths though.

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    Two votes for AK being louder... I say, "hmmm..."

    I don't have an AK, but I've been in some serious carbine training courses where the AR was more popular but there were still enough AKs represented. During more than one stage I was between one of each.

    I'd be hard pressed to say one was actually "louder" than the other, because the report from each is so different. The 5.56 is a much higher-pitched crack, not surprising considering its 40% higher muzzle velocity. The AK round is a lower-pitched sound (frequency content is lower) but due to the slower bullet velocity, the duration of the sound is longer than that of the 5.56. So higher-pitched and shorter duration may seem "quieter" to some ears than lower-pitched and longer-lasting.

    As humans age, we lose the higher-frequency end of our hearing range, so depending on who's doing the listening, that may also make the 7.62x39 round seem louder.

    Something else to consider is that the sound of each round will be perceived differently by the shooter versus an observer, and further by the observer's distance from the muzzle. The lower-frequency report of the AK round will propagate farther than that of the 5.56 round.

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    Ex Member Array Ram Rod's Avatar
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    About the same actually....out of a SBR with no muzzle brake. Most of this depends on where you are listening from. Behind the rifle, beside the rifle, or in front of the rifle, and your proximity.

  6. #6
    Distinguished Member Array BlueNinjaGo's Avatar
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    Quote Originally Posted by Ram Rod View Post
    or in front of the rifle
    If I'm in front of a rifle being fired, I'm not going to be paying attention to how loud it is...

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    VIP Member Array Kilowatt3's Avatar
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    I'm with Smitty - "Louder" is really subjective, given the difference in pitch. Personally, I find the 7.62 to be "louder", but the 5.56 is a lot more intrusive. I also suspect that the 5.56 is potentially more damaging to the ears, given the higher frequency.

    Just my $.02.

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    VIP Member Array paaiyan's Avatar
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    Quote Originally Posted by BlueNinjaGo View Post
    If I'm in front of a rifle being fired, I'm not going to be paying attention to how loud it is...
    Agreed!
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    New Member Array LoneWolf69's Avatar
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    Quote Originally Posted by gasmitty View Post
    Two votes for AK being louder... I say, "hmmm..."

    I don't have an AK, but I've been in some serious carbine training courses where the AR was more popular but there were still enough AKs represented. During more than one stage I was between one of each.

    I'd be hard pressed to say one was actually "louder" than the other, because the report from each is so different. The 5.56 is a much higher-pitched crack, not surprising considering its 40% higher muzzle velocity. The AK round is a lower-pitched sound (frequency content is lower) but due to the slower bullet velocity, the duration of the sound is longer than that of the 5.56. So higher-pitched and shorter duration may seem "quieter" to some ears than lower-pitched and longer-lasting.

    As humans age, we lose the higher-frequency end of our hearing range, so depending on who's doing the listening, that may also make the 7.62x39 round seem louder.

    Something else to consider is that the sound of each round will be perceived differently by the shooter versus an observer, and further by the observer's distance from the muzzle. The lower-frequency report of the AK round will propagate farther than that of the 5.56 round.

    Made things as clear as mud, didn't I? Spent too much time in the vibration lab!

    I was told even though the 5.56 is higher pitch, the sharper sound it creates makes it louder at a distance. Gunshots that are sharper always sound louder at a distance. Can that be true?

    Also don't both rounds echo quite a bit when fired off?

  10. #10
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    The sharper / higher pith bugs me more, so subjectively I do not like the 223, in sheer volume / decibels it is probably the 762...

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    VIP Member Array varob's Avatar
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    Standing behind an AK and an AR both being fired at the same time. The AK was drowning out the AR. Just my personal observation, no scientific data.
    Don't believe what you hear and only half of what you see!
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    New Member Array LoneWolf69's Avatar
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    Quote Originally Posted by varob View Post
    Standing behind an AK and an AR both being fired at the same time. The AK was drowning out the AR. Just my personal observation, no scientific data.
    I looked it up the M16 and AK-47 are both 163 dB while standing next to the shooter and the M4 is 165 dB.

    But the question is, which one sounds louder at a distance, the sharper crack of the 5.56x45 or the deeper boom of the 7.62x39?

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    Distinguished Member Array BlueNinjaGo's Avatar
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    Quote Originally Posted by LoneWolf69 View Post
    But the question is, which one sounds louder at a distance, the sharper crack of the 5.56x45 or the deeper boom of the 7.62x39?
    I would think that depends on the environment. Plus it's still just an opinion.

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    New Member Array LoneWolf69's Avatar
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    Quote Originally Posted by BlueNinjaGo View Post
    I would think that depends on the environment. Plus it's still just an opinion.
    If both weapons are fired in an urban or forest/mountain environment. Both setting have a lot for the sound to bounce off of.

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    the scientific answer...

    Two things to consider about sound waves, same as vibration: frequency, and amplitude. Most of what we hear, be it music, voice, noise, is a combination of many different frequencies at varying amplitudes.

    Taking the simplest case: if you had just two single-frequency sounds (like from two different tuning forks, or two notes on a piano), and each had the exact same amplitude, the lower-frequency sound would propagate farther.

    The problem in nature (real life) is that we rarely hear sounds from a single-tone source. Vehicle noise, music, gunfire - all contain a range of different frequencies all at different amplitudes. So the simple guidance is that for two different sounds which are generated at the same amplitude, the one with more lower-frequency content will propagate farther.

    When it comes to gunfire, it's difficult to assess true "loudness" because our ears don't behave in a linear fashion; they are biased more toward lower frequencies than high. So if we could physically arrange for our .223 and the 7.62x39 to have exactly the same sound amplitude, the 7.62 will sound louder because of its lower frequency content. From a distance, the 7.62 will sound louder.
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