Bullet speed vs. barrel length

    Results 1 to 8 of 8
    1. #1
      Junior Member
      Join Date
      May 2010
      Posts
      45

      Bullet speed vs. barrel length

      I have a question merely out of curiosity. A lot of ammuniton manufacturers are printing physical performance data on their ammuniton boxes (incl. velocity, energy, and trajectory) and in most cases the data are based on 4 inch test barrels. How do this performance data change with shorter or longer barrels. Let's do an example:

      Ammunition is a 9mm FMJ 115grains. Velocity (Muzzle) is 1135 Fps and Velocity (50 Yards) is 1027 Fps. Energy (Muzzle) Joule 446 and Energy (50 Yards) Joule 358 .

      How would those data change with
      1. 3.58 inch barrel with polygonal rifling
      2. 4.25 inch barrel with polygonal rifling
      3. 4.49 inch barrel with polygonal rifling

      And by the way: How much is the difference between a conventional rifled bore and a polygonal rifled bore of the same lengths when it comes to speed (roundabout)? Is it a slighty different or significant? I read that polygonal riflings have higher bullet velocity.

      I asked a couple of people but never got good answers. Of course they said as longer the barrel as faster the bullet and as shorter the barrel as slower the bullet. But how much slower will the bullet out of the above mentioned 3.58 inch barrel travel compared to the 4 inch barrel ?

      Maybe I should have not slept through all my physic courses in High School. LOL

      Thanks for your answers.

    2. #2
      TOF
      TOF is offline
      Senior Member TOF's Avatar
      Join Date
      Sep 2006
      Location
      Northern Arizona
      Posts
      3,015
      There is more to it than barrel length. Gun Powder comes in various forms and compositions. I have had loads using fast burn powder yield greater velocity from short barrels than long and the reverse.

      My friends 9MM Glock (poly barrel) and my 9MM M&P (conventional barrel) yield within 10 FPS or so of each other at 1100 FPS range. The glock may be faster today and slower tomorrow.

      If you try to fit things into simple rigid catagories you will be wrong 50% of the time.

    3. #3
      Junior Member
      Join Date
      May 2010
      Posts
      45
      hmmm....like I said, I am just curious. For example I wonder how much speed difference would be there between a 9mm USP and a 9mm USP Compact with the same ammo. How much speed diffence would make the difference 0.67 inches.

      So you would say with the on kind of ammo the bullet from the shorter barrel will travel longer, in another case the bullet from the longer barrel will travel longer?

    4. #4
      TOF
      TOF is offline
      Senior Member TOF's Avatar
      Join Date
      Sep 2006
      Location
      Northern Arizona
      Posts
      3,015
      As indicated above: (You have to think a bit) If the barrel is to long for the powder used the bullet will slow down when pressure from powder burn begins to drop before bullet exits barrel. In the extreme the bullet might not exit at all.

      If the barrel is to short for the powder used the bullet will exit before complete burn and maximum pressure, therefore velocity is reached.

      None of us know what powder the factories are using so can't answer your question.

      Empirical testing is required to derive the correct answer to your question because it could go either way with any given load.

    5. #5
      Member HGF Gold Member
      Join Date
      Nov 2010
      Location
      Indiana
      Posts
      501
      IMHO barrel length ballistics should be an ammunition research project. The manufacturers spend millions coming up with specific loads that work in short barrrels, long barrels, for target, hunting, SD. I believe it is a fast burn powder that is used in the shorter barrels. Using a round with a slower burn rate in the short barrel allows some of the powder to escape and ignite outside the muzzle with attendant flash and muzzle blast. I use Speer Gold Dot 38+P "Short barrel" in my 442 snubby.
      If you take the time, there is a wealth of information about ballistics from the manufacturers online. Pick one that "fits" your needs and don't sweat the barrel length. Look at bullet performance (expansion, ft/lbs. etc.) if SD is the goal.
      Eli
      PS...when I was Civil War reenacting I crewed a battery section that used a 3" Mountain Howitzer and a 3" Ordinance Rifle. Short tube/long tube. Well, the crowds seemed to love that little howitzer because of the boom and smoke rings (me too). Same charge in the big gun was neither as cool sounding or looking! Just an example, it was show-biz after all.

    6. #6
      Junior Member fiasconva's Avatar
      Join Date
      Jun 2009
      Location
      York County, VA
      Posts
      95
      Generally speaking, you are going to get about 50 to 70 fps more speed per inch of barrel length.

    7. #7
      Junior Member
      Join Date
      Jan 2009
      Location
      Missouri
      Posts
      32
      Here is a link that may give you an idea of how barrel length effects bullet velocity. It shows differences in barrels by inches with different ammo. As stated above, type of ammo, make and which way the wind is blowing in Fiji have effects on the results. http://www.ballisticsbytheinch.com/results.html

    8. #8
      Junior Member
      Join Date
      May 2010
      Posts
      45
      Thank you Gschnarr. That was exactly what I was looking for.

    Sponsored Links

    Posting Permissions

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

    Search tags for this page

    22lr auto match muzzle velocity from 5.5 inch barrel
    ,

    9mm barrel length velocity

    ,

    9mm muzzle velocity vs barrel length

    ,

    9mm velocity barrel length

    ,
    9mm velocity vs barrel length
    ,
    9mm velocity with 5 inch barrel and shoe=rter
    ,
    9mm vs 45 at 3feet
    ,
    accuracy difference between 3 1/2 barrel & 4 in simiauto pistol
    ,
    bullet drop on a 16 inch barrel 9 mm
    ,
    bullet velosity out of short barrels
    ,
    handgun barrel length performance
    ,

    handgun barrel length vs velocity

    Click on a term to search for related topics.