.308 16 inch or 18 inch Barrel?

This is a discussion on .308 16 inch or 18 inch Barrel? within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; I figure this wouldn't be a bad place to post this since I know that there are plenty of subject matter experts here, well here's ...

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Thread: .308 16 inch or 18 inch Barrel?

  1. #1
    Member Array paratroop23's Avatar
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    Question .308 16 inch or 18 inch Barrel?

    I figure this wouldn't be a bad place to post this since I know that there are plenty of subject matter experts here, well here's my situation........

    I'm planning on buying a .308 Battle Rifle. Most likely an HK G3 clone, PTR91 to be exact. I'm torn between the 16 inch and the 18 inch barrel. I want to be able to reach out and touch targets out to at least 450m, and be to be able to use it in an urban enviornment if it's ever nessesary ie clear rooms, deploy it easily from vehicles etc etc. I'm looking at collapsable or folding stock options, but anyway....how much am I losing by going from an 18 to 16 inch barrel? Will it make much of a difference in range and/or power once steel reaches target?

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  3. #2
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    You'll lose around 200 FPS.

    If it were me, I'd go with the 18 incher. Its not that much different when it comes to handling, but on a .308 you start getting a lot of muzzle flash and very loud sound. Enough flash that you would light up a whole room with it.

    In the dark when things are tough, muzzle flash is not your friend.

    I doubt that the recipeint would notice the 200 FPS or so difference though.
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    Senior Member Array glock21guy's Avatar
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    I have a AR-10 with a 20 inch, and from what I am told. Standing on the side it is loud. Shooting the thing is not as loud as I would have thought, but it gets your attention. By the way I am shooting outdoors.

    Go with the 18 inch.
    Aaron

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    Distinguished Member Array AKsrule's Avatar
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    I have a DSA Fal and a Cetme ; Both have 16" barrels with Muzzle
    Brakes.

    When you are BEHIND the rifle you don't notice the Noise

    The advertised velocities for .308 are usually about 2800 fps for a
    150gr bullet from a 24" barrel.

    IMHO - you Do lose about 200fps by going to a 16"
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    VIP Member Array Bud White's Avatar
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    Quote Originally Posted by AKsrule View Post
    I have a DSA Fal and a Cetme ; Both have 16" barrels with Muzzle
    Brakes.

    When you are BEHIND the rifle you don't notice the Noise

    The advertised velocities for .308 are usually about 2800 fps for a
    150gr bullet from a 24" barrel.

    IMHO - you Do lose about 200fps by going to a 16"

    I have the Cetme and as said when your behind it you don't notice it

    Course i don't notice it on my Muzzle braked 300 mag either but those around you do

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    Senior Member Array Chuck R.'s Avatar
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    Guys,

    The velocity loss for a .308 isn't that bad, certainly less than 50FPS per inch. Here's some references:

    The Remington Catalog 2003 includes a "Centerfire Rifle Velocity Vs. Barrel Length" table that shows the following velocity changes for barrels shorter or longer than the test barrel length:

    MV 2000-2500 fps, the approximate change in MV per 1" change in barrel length is 10 fps.
    MV 2500-3000 fps, the approximate change in MV per 1" change in barrel length is 20 fps.
    MV 3000-3500 fps, the approximate change in MV per 1" change in barrel length is 30 fps.
    MV 3500-4000 fps, the approximate change in MV per 1" change in barrel length is 40 fps.


    The 45th Edition of the Lyman Reloading Handbook also has a table showing Center Fire Rifle Velocity Vs. Barrel Length. Their figures apply to barrels between 20 and 26 inches in length and agree with the Remington figures. The Lyman table shows the following approximate velocity changes:

    For rifles with muzzle velocities in the 1000-2000 fps range, the change in velocity for each 1" change in barrel length is 5 fps.
    For rifles with muzzle velocities in the 2001-2500 fps range, the change in velocity for each 1" change in barrel length is 10 fps.
    For rifles with muzzle velocities in the 2501-3000 fps range, the change in velocity for each 1" change in barrel length is 20 fps.
    For rifles with muzzle velocities in the 3001-3500 fps range, the change in velocity for each 1" change in barrel length is 30 fps.
    For rifles with muzzle velocities in the 3501-4000 fps range, the change in velocity for each 1" change in barrel length is 40 fps.

    The 43rd edition of the Lyman reloading Handbook gave some concrete examples of velocity loss for specific calibers and loads. The Lyman technicians chronographed some high velocity cartridges in rifles with barrels ranging in length from 26" down to 22" with the following results:

    The average loss for the .243 Win./100 grain bullet was 29 fps per inch.
    The average loss for the .264 Win. Mag./140 grain bullet was 32 fps per inch.
    The average loss for the .300 H&H Mag./220 grain bullet was 25 fps per inch.

    For standard high intensity cartridges in the same test, the Lyman technicians chronographed the cartridges in barrel lengths ranging in length from 24" down to 20" with the following results:

    The average loss for the .270 Win./130 grain bullet was 37 fps per inch.
    The average loss for the .270 Win./150 grain bullet was 32 fps per inch.
    The average loss for the .300 Sav./180 grain bullet was 17 fps per inch.
    The average loss for the .30-06/180 grain bullet was 15 fps per inch.
    The average loss for the .35 Rem./200 grain bullet was 11 fps per inch.


    I've got a 19" on my DSA SA58 Para FAL, mostly due to balance. To tell you the truth, I don't find a 16" barrel that much handier over an 18" barrel enough to justify the extra noise.

    Chuck
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    I'd go with 18" my FAL has a 20" barrel.

    Either way I'm not going to clear houses with my FAL. I might shoot through them but I'm not going to clear them.
    “You can sway a thousand men by appealing to their prejudices quicker than you can convince one man by logic.”

    ― Robert A. Heinlein,

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    Distinguished Member Array Bob The Great's Avatar
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    Quote Originally Posted by paratroop23 View Post
    I figure this wouldn't be a bad place to post this since I know that there are plenty of subject matter experts here, well here's my situation........

    I'm planning on buying a .308 Battle Rifle. Most likely an HK G3 clone, PTR91 to be exact. I'm torn between the 16 inch and the 18 inch barrel. I want to be able to reach out and touch targets out to at least 450m, and be to be able to use it in an urban enviornment if it's ever nessesary ie clear rooms, deploy it easily from vehicles etc etc. I'm looking at collapsable or folding stock options, but anyway....how much am I losing by going from an 18 to 16 inch barrel? Will it make much of a difference in range and/or power once steel reaches target?
    IMO, 2in won't make that much difference in handling the gun. I have an 18" PTR-91, and I was actually surprised at how small it was. I guess I was envisioning a giant shoulder cannon, but it's really not all that big. It is muzzle-heavy though, much more so than my AR, and for that reason, it might not be the best to clear your house with (besides the eardrum shattering enclosed blast, blinding muzzle flash, and the fact that as far as the round is concerned, your house might as well be made of tissue paper).

    But, back to your original question, the 18" barrel isn't going to make the gun an elephant rifle any more than the 16" barrel makes it a pea shooter. Ballistically, I would be very surprised if there's a significant difference.

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    Well, it's hard to beat the preliminary research that the Israelis did on the Galil rifles before they built them and in the .308 version the available barrel lengths are 15.8" ~ 18.1" ~ and 20" - so pick your poison.
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    Hey Chuck...

    The figures you put out more than likely were for bolt action rifles. For gas operated semi autos, the velocity loss per inch is much more severe.

    Fact of the matter is, unless you chronograph both rifles using identical loads, its pure speculation.

    The chronograph will surprise you. Awhile back we did several brands of AR's at the range. We did some 20 and 16 inchers and compared them to each other. You would think that the guns would be close right ? Wrong.
    Some builders use different gas ports and that makes alot of difference. Some are .062, some are .090 and some are .125 diameters on the gas ports.

    There has been alot of discussion on the velocity loss aspects of troops using 14.5 barrels verses the 20"s. Its certainly more than the 30 FPI stated because the gas ports are usually opened up for more reliable operation. Also the powder burn rate makes a big difference. If its a fast powder that burns in a short amount of time, chopping off a long barrel wont change things much. If its a slow burning powder that needs all of the barrel length it can get, cutting it back can make a huge difference.
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  12. #11
    Distinguished Member Array AKsrule's Avatar
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    To Add Some Perspective;
    The .300 Savage ( a very respected midrange Deer Hunting round in its day ) used a 150 gr. bullet at 2600 fps.
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    Senior Member Array Chuck R.'s Avatar
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    HotGuns,

    I own an Ohler 35P chronograph, so yes I've done some chronographing. Each barrel is a law unto itself in that some are fast, some are slow, but still a 200 FPS loss for 2 inches going from 18-16" is still a bit of a stretch especially in the .308s velocity range. The guys over at the FAL Files chopping down to 16" and opening ports don't report that much of a loss.

    I've chronographed my FAL with the gas on and gas off, really not much of a difference at all between the two means. I've also done some research and from what I've read the difference or performance lost due to gas operation is minimal and not worth worrying about. IF it was it would be listed as a "feature" on every bolt action rifle

    Anyhow, IF he goes with the HK, there's no gas ports to be concerned with.

    The 5.56 loses more per inch because it has a higher MV to begin with and also MV loss isn't linear as in a constant 30-50 per inch. At some point you cut into a more pronounced portion of the pressure curve and the barrel shortening has a much greater effect.

    Chuck
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    Member Array paratroop23's Avatar
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    Thanks. So from what I'm gathering is that there isn't much of a difference between 16 inch and 18 inch, but most prefer the longer of the two.

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    Senior Member Array cmidkiff's Avatar
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    Either barrel length will do what you need it to do. Good choice, by the way, I'm happy as can be with my (16") PTR91. Here's a shot of my daughter getting it on target :)

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  16. #15
    Member Array paratroop23's Avatar
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    Quote Originally Posted by cmidkiff View Post
    Either barrel length will do what you need it to do. Good choice, by the way, I'm happy as can be with my (16") PTR91. Here's a shot of my daughter getting it on target :)

    Pretty cool!! Is it pretty accurate? I've heard nothing but good things!!

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