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Barrel/Velocity Question

Discussion in 'Rifle Country' started by blackops, Dec 31, 2009.

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  1. blackops

    blackops Member

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    I've always been under the impression a longer barrel does give you a little more velocity, but lately I've come across a few people that have disagreed. I would think if two people have identical rifles and identical cartridges, but one has a 20" the other a 26" the guy with the 26" is going to have an extra 200fps or so. Am I wrong here?
     
  2. matrem

    matrem Member

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    Powder burn rate is a major factor in that.
     
  3. R.W.Dale

    R.W.Dale Member

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    No


    Sure from time to time you might have one 22" bbl that may be "faster" than one of your other guns with a 24" But don't let this fool you this is due to the differences between two different barrels aside from length.

    IE if you take a long barrel and cut it down you'll ALWAYS see a velocity loss with whatever load you test

    http://www.accuratereloading.com/223sb.html

    NO IT IS NOT! how many times does this myth have to be busted?
     
  4. matrem

    matrem Member

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    Not a myth.
     
  5. R.W.Dale

    R.W.Dale Member

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    YES YES it is!


    Compare any data you wish that shows loads for rifles and hand cannons and you'll find that 9 times in 10 the top performing powders for a 24" rifle are still the top performers in a 15" encore




    take hodgdon's data for 308win shooting 150grn bullets

    In a 24" rifle varget is the top performer @ 2937fps
    in a 15" handgun varget is still the top performer @ 2675fps

    NOW note that a fast for 150g bullet powder like H-322 doesn't perform too hot in a rifle
    the top H-332 rifle load is 2702 fps

    so by conventional wisdom this fast powder will do better in a handgun...........NOPE


    from a 15" hand cannon h-332 only gets you 2471fps compared to over 2600 with varget
     
    Last edited: Dec 31, 2009
  6. matrem

    matrem Member

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    Well..
    My chronographs have "said" otherwise.
    Usually with regard to .357 & .44 mag in leverguns.
    And they use far faster powder than "expected' for that bbl length.
     
  7. R.W.Dale

    R.W.Dale Member

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    aren't you using what's considered "slow" handgun powders to get top performence in any barrel length?

    if you load .44 mag with ww231 do you expect more velocity from a handgun than a big old stiff charge of ww296. no of course you don't

    You match the burn rate to the CARTRIDGE pressure rating,case capacity and expansion ratio. Barrel length is quite literally well after the fact
     
  8. taliv

    taliv Moderator

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    ...to a point, of course. i mean, theoretically, if you were shooting a 223 from a 60 foot long barrel, the projectile would be gaining speed for a while, then start losing and i doubt it would make the end of the barrel.
     
  9. blackops

    blackops Member

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    So what length barrel would a .223, 243,270, 308etc lose velocity? Normal rifles are in the 20"-26" range yet I've seen some 30". So when is length just too much? Obiously you want a length managable to carry and especially hunting, but I'm interested to what the breaking point is for length.

    + I thought slower burning powders give you more velocity as well. Still, will an extra 4" on your barrel give you that extra velocity?
     
  10. Clipper

    Clipper Member

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    I don't have more than 22" on any rifle I own, and that's a Mosin-Nagant 91/30 I cut down. My .257 Roberts AI is 21". I recently cut my Winchester M-12 to 20" for slug hunting. The Hi-Point carbines have 16" barrels, and the velocity difference is negligible for 9mm vs a 5" pistol barrel. I still can't talk my wife into shortening her Savage 99 (.300sav) or her Rem 141 (.35rem) from 24" to a more handy 20", but I'll keep working at it...
     
  11. AR-15 Rep

    AR-15 Rep Member

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    i'm kind of curious about those calculations as well.
     
  12. bpl

    bpl Member

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    I believe I've read that the .22lr begins to loose velocity somewhere in the 16"-18" barrel length range.
     
  13. R.W.Dale

    R.W.Dale Member

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    Here's what 6mmbr has to say on the matter
    http://www.6mmbr.com/308Win.html

    notice our old friend varget is listed again even for 30"+ barrels

    [​IMG]
     
  14. AR-15 Rep

    AR-15 Rep Member

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    Thanks...
     
  15. Uncle Mike

    Uncle Mike Member

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    never never land...never land here!
    It has to do with the 'peak pressure' being reached while the bullet is still in the barrel.

    If your still burning powder and the pressure has not reached its maximum, and the bullet leaves the barrel, then no more pressure to act on the bullet.

    If the bullet stays in the barrel until the pressure has maxed out, the bullet has been pushed as fast as it is ever going to be.

    As the 6mmBR article says, yes!
     
  16. Howard Roark

    Howard Roark Member

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    I know the shorter the barrel the less velocity. I also would know those ugly rifles anywhere. They belong to John Whidden. He uses a 34" blank and backbores the muzzle 2". This way he doesn't have to turn the muzzle down to accept the sight band. Turning down the muzzle diameter opens the barrel diameter where you don't want that the most.
     
  17. rangerruck

    rangerruck Member

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    dude above is right on 22lr's; after 16 inches, you bullet starts to slow down, while inside the bbl.
    it all depends on what you are fireing as for a cartridge, and what is going to be it's usage. I think I read somewhere, to max out a 308 cartridge, where it won't gain any more velocity, you need a 38 inch bbl, after that , the bullet will start to slow down in your tube.
    who the hell could even use a 38 inch bbl? Could you properly even see a front site mounted on that? how fat around would your bbl have to be, to stop bbl droop, or sagging from heating up? How thick and heavy then, would your receiver have to be, to keep that bbl in proper alignment?

    So really it is a trade off; even for the 1000 yd shooters, who don't frickin move when they are on the line, I've never seen a tube longer than 30 inches myself, in person.
     
  18. mshootnit

    mshootnit Member

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  19. Caliper_Mi

    Caliper_Mi Member

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    We used barrels over 40" in the Revolutionary War... http://en.wikipedia.org/wiki/Brown_Bess A heavy profile octagonal barrel probably keeps it more rigid, but you've gotta be a heck of a man to fire that thing offhand without a bipod or something!

    I expect that the problems with barrel strength and harmonics keep benchrest shooters from going too long however.
     
  20. Clipper

    Clipper Member

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    We also used black powder...Completely different animal.
     
  21. nicholst55

    nicholst55 Member

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  22. CountGlockula

    CountGlockula Member

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    I need to pull out my 16 and compare with a 20 inch AR15.
     
  23. elmerfudd

    elmerfudd Member

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    With just about any bottlenecked cartridge you will always lose velocity by making the barrel shorter.

    With some very low powered cartridges, (like .22 CB's or Aguila caps), however you very well might see decrease in velocity with a longer barrel.
     
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