Barrel length - make much difference in power?

Barrel length - make much difference in power?

This is a discussion on Barrel length - make much difference in power? within the Defensive Carry Guns forums, part of the Defensive Carry Discussions category; Let's say I have a typical 9mm round, and I fire it in barrels of varying lengths. Say, for example, 3", 4", 5" and 6" ...

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Thread: Barrel length - make much difference in power?

  1. #1
    Senior Member Array Chevy-SS's Avatar
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    Barrel length - make much difference in power?

    Let's say I have a typical 9mm round, and I fire it in barrels of varying lengths. Say, for example, 3", 4", 5" and 6" barrel lengths are used in the test.

    Is there much difference in muzzle velocity and bullet energy?

    thanks
    'Be careful, even in small matters' - Miyamoto Musashi


  2. #2
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    It depends on the load and some other factors, but in short, yes it does.

    The longer the barrel the more it takes advantage of the burning powder to push the bullet forward... and long as the explosion is contained and powder to be burned, the bullet is getting faster... soon after it leave the barrel and no longer has gasses pushing it, the bullet begins to slow down.
    "Just blame Sixto"

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    Quote Originally Posted by SIXTO View Post
    It depends on the load and some other factors, but in short, yes it does.

    The longer the barrel the more it takes advantage of the burning powder to push the bullet forward... and long as the explosion is contained and powder to be burned, the bullet is getting faster... soon after it leave the barrel and no longer has gasses pushing it, the bullet begins to slow down.
    .
    But since we are in CC gun subforum, I will say this though. At the range you would be using your CC piece, it won't matter whether your gun has 3" or 5" barrel. If you start shooting at distances where that extra 2" will matter, you will have some explaining to do to your peers.

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    Senior Member Array Chevy-SS's Avatar
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    Yes, I agree with both of you.



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    As a general "rule of thumb," I use the figure of 30fps per inch of barrel length at the muzzle. Again, at practical ranges, not much difference.

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    VIP Member Array pogo2's Avatar
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    Here is an estimate

    Here is an interesting graph I found on the web, from Guns Magazine, that shows 9mm velocity vs. barrel length.

    Graph of 9mm velocity vs. barrel length

    I tried to read the points on the graph and here is what I got:

    6 inch barrel.....1400 fps
    5 inch barrel.....1320 fps
    4 inch barrel.....1230 fps
    3 inch barrel.....1150 fps

    The 3 inch barrel produced about 82% as much velocity as the 6 inch barrel. Since energy varies with velocity squared, I'd guess that the 3 inch barrel would produce about 67% of the energy of the 6 inch barrel.
    Firearms are second only to the Constitution in importance; they are the Peoples' Liberty's Teeth." - George Washington

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    VIP Member Array AZ Husker's Avatar
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    And when you're talking about ammo that needs a certain power factor to expand properly, that 67% can be a HUGE factor in a successful defensive shooting.

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    Senior Member Array Chevy-SS's Avatar
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    Quote Originally Posted by pogo2 View Post
    Here is an interesting graph I found on the web, from Guns Magazine, that shows 9mm velocity vs. barrel length.

    Graph of 9mm velocity vs. barrel length..............

    Very interesting. I wonder if anyone has done penetration tests?

    Thanks for the info
    'Be careful, even in small matters' - Miyamoto Musashi

  9. #9
    VIP Member Array AZ Husker's Avatar
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    Chevy...there is a huge disparity between penetration and expansion. If you want a projectile to simply pierce through the body, stay with ball ammo. If you want the maximum crush cavity and fatal damage, study the different defensive ammo. The problem with short barrels is they often don't give the best HP ammo enough velocity to reach the required speed to properly expand.

  10. #10
    Senior Member Array Chevy-SS's Avatar
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    Quote Originally Posted by AZ Husker View Post
    .....The problem with short barrels is they often don't give the best HP ammo enough velocity to reach the required speed to properly expand.
    Yeah man, this is why I'm asking. I'm looking at a new CC pocket gun, but wanna make sure it'll perform adequately.

    Currently using AMT .45 for CC,which is small - but it's stainless and very heavy. I want something lighter.

    thanks
    'Be careful, even in small matters' - Miyamoto Musashi

  11. #11
    VIP Member Array AZ Husker's Avatar
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    From my research, the 4" is the very minimum to obtain probable knock-down power from a reputable .45HP. The longer, the better. I don't carry pocket guns, but have no problem at all carrying either a Commander or 5" 1911 with a quality IWB rig.

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    Senior Member Array jualdeaux's Avatar
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    Quote Originally Posted by AZ Husker View Post
    The problem with short barrels is they often don't give the best HP ammo enough velocity to reach the required speed to properly expand.
    Which is why Speer came up with their Short Barrel designs.

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    Distinguished Member Array AKsrule's Avatar
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    Quote Originally Posted by pogo2 View Post
    Here is an interesting graph I found on the web, from Guns Magazine, that shows 9mm velocity vs. barrel length.
    I tried to read the points on the graph and here is what I got:

    6 inch barrel.....1400 fps
    5 inch barrel.....1320 fps
    4 inch barrel.....1230 fps
    3 inch barrel.....1150 fps
    Never count on advertised values when combining commercial ammo with a
    2 or 3 inch gun.

    Chronograph it ( or get it done by someone )
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    9mm and .40 loads are optimized for 4" barrels. .45 loads are optimized for 5" barrels. The difference matters. I would use a 3" 9mm or .40, but I would not use a 3" .45.

  15. #15
    Senior Member Array the_fallguy's Avatar
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    This is a really interesting thread so far. Does anybody have any reliable stats to show a difference in transfer of energy to the target between one bbl length and the next?
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