24" vs 26" vs 30" barrel .223

Discussion in 'Small Stuff--22s, 20s, and 17s' started by mattri, Dec 4, 2009.

  1. mattri

    mattri

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    What is the accuracy difference in these barrrel lengths?

    Other than portability, what factors affect choosing a barrel length?

    Thanks, Matt
     
  2. DukeDuke

    DukeDuke

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  3. manitou210

    manitou210

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    Jerry thanks for sharing your post it was extreemly well done
    and very informative. Many shooters building 223 with long barrels for F class shooting in Canada. I will sure pass on to them your results.
    manitou
     
  4. Laurie

    Laurie

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    Long-range target shooters, and some long-range varminters, go for the longer barrels solely for velocity. With any given bullet and its BC range, velocity at the far end of the flight is determined by the initial (muzzle) velocity.

    Also, wind deflection at any given range and set of wind conditions is determined by the combination of MV and bullet BC. So a high BC bullet at high MV moves less in the wind which means fewer dropped points taking that shooter's wind reading skills into account - nobody reads a tricky wind perfectly for every shot, even national team members.

    Whether all this matters depends on the discipline, cartridge and range. Palma, Fullbore (Target Rifle as we call it in the UK and British Commonwealth), and F/TR are limited to .308 Winchester and .223 Remington. 0.308" 155gn bullets need around 3,000 fps MV to be sure of staying supersonic at 1,000 yards, so a typical rifle for these disciplines has a 30" barrel minimum, sometimes up to 34", to get the necessary MV.

    The downside of length is weight, as all of these disciplines have weight limits. F/TR which has the highest at just over 18lbs including bipod sees the shooters have to choose between barrel length and profile, scope model etc to stay within the limit. Accuracy comes from a heavy profile barrel, but add that to 30" or more length and it's very heavy - that's why you have the 'Palma' barrel profiles that are heavy at the breech end for about 6", then have a steep taper down to a smaller diameter.

    You're talking about .223 Rem where barrel length has less effect on velocity than in larger cased cartridges. There is very little velocity gain by going above 30", and you don't lose much by dropping to 28".

    If you're not shooting at very long ranges, say at 600yd max, you really don't need a super-long barrel. 26" is probably all you need, and go for a heavy profile instead which makes it stiffer, hence likely to be more accurate.

    Incidentally look at some pics of the short-range benchrest guns in the main site. Since they are used at 300 yards tops, and there are weight limit issues, you'll see they are built with short (20" or even less) but very fat barrels - accuracy beats velocity in this game.

    Laurie,
    York, England
     
  5. Rust

    Rust

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    Barrel length does affect accuracy. The amount of barrel deflection from vibration is greater in a longer barrel. This is one reason why low ES/SD numbers are important so that the bullet consitantly exits the muzzle at the optimum time in the vibratory patter, the "accuracy node". This is one reason why short range bench resters tend towards short stiff barrels, for the smaller amount of deflection.

    Increased barrel length past a certain point gives diminishing velocity returns, something rimfire shooters have known about for years. As gas pressure decreases as the bullet travels down the barrel, at somee point the drag of the bullet in the bore exceeds what the remaining energy in the gas can do and velocity actually decreases. In a subsonic match rimfire round, this occurs at or under 18". In a .223 with the very heavy bullets this can occur at or past 32"

    Like everything else involved in accuracy shooting, it's a matter of achieving the best compromise for maximum performance of the shooting system as a whole.

    In my long range rifles, there are loads that are more accurate at 100 yards, but have larger ES/SD numbers which show up as excessive vertical at 1,000, or a load with great accuracy and good ES/SD numbers but with too slow a velocity which will show up as excessive wind drift at 1,000.

    Generally I want a combination that will produce 2950 fps with my preferred bullets, and ES/SD numbers in the single digit range. If I can achieve that with a shorter barrel all the more better. Given two barrels can achieve the same target velocity and ES/SD numbers. I'll take the shorter stiffer barrel to minimize vibratory muzzle deflection.

    Now in a non-weight restricted class with a large capacity case, you can use a truck axle for a barrel as long as you can find and hopefully end up without the compromise balancing act, or at least not as much.

    Personally, I'm going with 28" on the new .223, and rebarreling to 28" with the .308. Ah yes, two on going projects at the same time ;D
     

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