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Thread: Fast twist barrels

  1. #1
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    Fast twist barrels

    Question , Does a faster twist barrel ( 1-8) push bullets at a higher velocity than a 1-12 twist barrel. One rifle a 16 inch XBolt 223 the other a Rem Mod 7 20 inch barrel 223, both rifles using exact same load?
    Haven't had a lot of experience with faster twist barrels so interested to see what people think.
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  2. #2
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    Not faster velocity, but faster spin obviously, which provides greater stability at longer range


    Sent from my iPhone using Tapatalk

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    Almost literate. veitnamcam's Avatar
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    No it shouldn't all other things being equal.
    In theory if anything it should be slower as using more of the energy to rotate the projectile faster.
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    and by spinning it faster it should expand faster/more explosively......

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    Thanks for the replies, Beeman has picked up a 16 inch XBolt and is trying different loads to find a nice accurate load. I said to him that the 60 gr loads he was trying would be on the slow side ,maybe. Anyway the other day we took it out and run some loads through the Chrono plus to see how slow they were going, surprise, suprise, they were honking it.
    The fastest 60 gr load went through at 2948 fps, very good, then we tried the normal old load of 55 gr Hornady with 25 grs BM 2 and they were cruising at 3103 and 3090 fps ( only had 2 left to try).
    Now my 20 inch Rem Mod 7 shoots the same 55 gr Hornady load at about 2950- 3000 fps. Not sure if mine may be one of those slow barrels but that little XBolt is a grunty ,short , package .

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    The 20 inch barrel should be faster than the 16inch. Which one is the fast twist?

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    I was sort of expecting about 120 fps slower than my velocity but it's just about the other way round his rifle appears to be up to 150 faster than mine using the same loads. Very interesting stuff.

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    Quote Originally Posted by Cigar View Post
    The 20 inch barrel should be faster than the 16inch. Which one is the fast twist?
    The 16 inch X bolt

  9. #9
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    not necessarily....once all the powder has burnt,a longer barrel slows the projectile down...WHY 22lr is hard to keep subsonic with really short barrel....
    definately a longer barrel will be faster with large amount of powder to burn....7mm mag etc...but a 223 only NEEDS something like 16-18" to have complete burn....
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    Maybe a smaller chamber in the fast twist (so more pressure, therefore higher velocity).
    Probably easy enough to check by dropping a case fired in the Remmy into the X-bolt.
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  11. #11
    Almost literate. veitnamcam's Avatar
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    Lots of things could affect it.... The Rem probably has a looser chamber and or more freebore lowering preasure and hence velocities.
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    Greetings All,
    I have not seen any evidence presented to suggest that a faster twist increases velocity. There are two .223 rifles in my cupboard, one 12" and one 8" twist. Velocities are about the same once barrel length is allowed for. The 26" barrel 12" twist gives about 80 fps more than the 570mm 8" twist barrel pretty much what you would expect. Differences due to other variables can be much larger. Case capacity, powder lot, chamber variables and many others all have an effect on velocity. Over the last few years I have been doing some test firing with some of my rifles, initially looking at powder lots in the 6.5 and more recently different powders and different projectiles in the .308. More tests on different powders and cases in the .223 and different case weights in the .308 are still in the blocks waiting to be shot. I am only using ADI powders and so far have found most but not all of the Hodgdon/ ADI data to be pretty good.
    Will report more later. Regards Grandpamac.
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  13. #13
    Member Magnus's Avatar
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    My understanding of barrel twist rates are really only to do with the projectile stability not to do with velocity.
    Drink Beer.

  14. #14
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    Quote Originally Posted by Micky Duck View Post
    not necessarily....once all the powder has burnt,a longer barrel slows the projectile down...WHY 22lr is hard to keep subsonic with really short barrel....
    definately a longer barrel will be faster with large amount of powder to burn....7mm mag etc...but a 223 only NEEDS something like 16-18" to have complete burn....
    Not quite that assumes that all energy from burnt powder is instantly passed on to the projectile but realistically it has intertia and take time to accelerate similar to dropping a bullet from a high building. It doesn't instantly reach terminal velocity. Just because all the powder is burnt doesn't mean acceleration stops. The bullet will still accelerate until the force from the pressure of the xplosion is equal and opposite to the drag from the barrel and air. If you want to see this go run a few loads though quickload etc. Complete burn is not the same as max velocity. Ie why you will see 7mm08 and 6.5 creedmoors with 30 inch barrels etc for target.
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  15. #15
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    Here’s article from Accurate Shooter on the topic Twist versus Velocities.

    How Muzzle Velocity Changes with Different Barrel Twist Rates « Daily Bulletin

    And here’s Frank Green's (co-owner Bartlein Barrels) comment that he posted on the Oz F Class forum re that article.

    Not only did we make all those barrels in the test but we chambered them as well. So same chamber reamer was used in all of them and the barrels where all made at the same time. If I recall correctly all of the barrels where made out of the same lot of material except for the left hand twist was out of a new lot. So about as identical as you can make them.

    It's always been my understanding that twist might have a small impact on velocity but for the most part it really doesn't in the grand scheme of things.

    Later, Frank
    Bartlein Barrels”

 

 

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