GUN Tell me about barrel lengths.

Discussion in 'On Topic' started by Irom, Mar 15, 2009.

  1. Irom

    Irom OT Supporter

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    I was looking at buying my first rifle and I was wondering how different barrel lengths effect range and accuracy and all that. I know next to nothing about firearms.
     
  2. GarandBobcat

    GarandBobcat New Member

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    Okay, this will be the quick-and-dirty version.

    In general, the longer the barrel, the higher the velocity you obtain from a given cartridge, since the longer barrel gets a longer contained powder burn. This is only true, though, up to a certain point, after which the burning powder's "push" is less than the friction of the bullet's travel down the bore.

    More velocity means your zero range can be longer--the arc of the bullet's travel is relatively flat for a greater distance, so your sights can be set for POI=POA somewhat farther out, meaning you get a little more engagement range for a set sight-in.


    Also, for iron sights, a longer barrel generally means you can have a longer sight radius. That is, the front and rear sights are farther apart. This doesn't make the gun any more mechanically accurate (i.e. if you put it in a vice and fired it, using only a single cartridge loading, the longer barrel wouldn't necessarily produce smaller groups than the shorter barrel) but it does make it easier for a person, when aligning those sights, to shoot accurately.

    Then there's the matter of handiness. A shorter barrel gun is going to be lighter, all else equal, and easier to tote around/swing onto target, than one with a longer barrel.

    But, a shorter barrel tends to make the gun louder, and increase the flash (see the first half of Point 1, about powder burn space) and recoil upon firing (less weight and Newton's Third Law, gun has more "free recoil velocity").


    So to summarize:
    Longer barrel: heavier, higher velocity, longer useful range (up to a point), and easier to be accurate with iron sights.

    Shorter barrel: lighter, handier, not so high velocity, less long useful range, slightly less easy to be extremely accurate with irons (though still capable of very good accuracy), slightly louder and creates more flash.

    If you're going to be doing from-the-bench range shooting, might as well go for a longer barrel. Or if you're going to be shooting CMP/NRA High Power matches and the like, especially with iron sights.

    If you're going to be toting this rifle around a lot, using it in the field, and using optics, you may be just as well-served (if not slightly better) with a shorter barrel.
     
  3. Jas0n

    Jas0n Антихрист

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    What kind of rifle are you talking about, and what do you plan to do with it? Is this a hunting rifle? What will you be hunting? And so forth.
     
  4. sp00n155

    sp00n155 You underestimate the insignificance of my penis OT Supporter

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    hold on a second while I run calculations to figure out what you're doing with the rifle
     
  5. fatmoocow

    fatmoocow bored OT Supporter

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    If you're looking at AR's for example the difference between 16" and 20" is about 150 feet per second, which isn't much, but at your max range the 150 fps may be the difference between fragmenting or pin holing.

    Also for a given cartridge there is going to be a theoretical length that is most accurate. Shorter barrels to a degree are more accurate because they are inherently stiffer, but shorter barrels are inherently less accurate because the bullet has less time to stabilize. So a 18" 308 is often more accurate than a 24" and usually more accurate than a 10" but it depends on a lot of factors.
     
  6. Carl Brutananadilewski

    Carl Brutananadilewski Active Member

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    size doesn't matter, it's how you use it :hsugh:
     
  7. purebad

    purebad I don't need your approval, right?

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    ibmineislongerthanyours
     
  8. phrozenlikwid

    phrozenlikwid New Member

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    GarandBobcat pretty much gave you a good cliffs version.

    Unless speed is of considerate value to you (IE, you better be reloading trying to push long/heavies faster and faster), shorter is muuuuuuuch easier to deal with. Unless I was shooting a LR sport that necessitated it, I'd go shorter.
     
  9. Irom

    Irom OT Supporter

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    I'm looking to buy an M1A for nothing else other than to have it before it becomes illegal, frankly. I did some reading and I don't think the previous assault weapons ban included models like the M1A, but I'd still like one. I don't plan on hunting with it.
     
  10. PorscheRacer

    PorscheRacer You see this? It means not welcome

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    Don't worry they'll try to ban it with the new AWB
     
  11. THT

    THT The easy way is always mined

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    If a new one comes, it'll be broader than the 94 ban and permanent.
     
  12. Irom

    Irom OT Supporter

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    Anyone have any experience with the M1A? Or have any better suggestions?
     

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