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How long can (should) a barrel be...?

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I thought this was a cool article. My takeaway is 30-34” is about it for a .308 as the muzzle velocity won’t significantly change out to 6’ long. But someone actually built a 6’ long .308 to tell us that!


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Yes - you can have it too long. 😁
 
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That barrel probably bows like a wet noodle in the middle. 😁 There is such a thing stiffness versus length not just applicable to rifles.
 

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What length barrel does Federal use to test their .308 Gold Medal Match? Their website states Muzzle Velcoity @ 2650 fps, which we know to be "average" and all. The Marine Corps and Army used 26" Remington's for years to get the most out of the .308's effective range. Didn't they go to a shorter barrel with ther newer sniper rifles? Improvements to ballistics with bullet design, improved powder nad barrel metallugy is probably why shooters can get better accuracy with shorter barrels. Ammirite?

Jarhead
 

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The M14 has a 22" barrel and some outstanding scores have been fired with them at 1000 yards. Most .308 sniper rifles (M24 and M40) have 24" barrels and we know they have excellent accuracy. A lot has to do with diameter. Medium and heavy barrels tend to exhibit more consistent accuracy. My 18.5 inch LRB M25 shoots about as good as anything out to 800 yards (I haven't shot it at 1000).
 

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I'd like to see some high-speed video of the barrel harmonics on that 88" long tube! I'll bet that it whips around like a wet noodle! The Germans (and probably others) made some cannon tubes so long that they required a trestle to minimize barrel droop. IIRC, the infamous 'Paris Gun' was one such.

Palma shooters at least used to prefer longer than average barrel lengths. Seems like 28-30" were common on those guns. That may have changed in recent years.
 

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I think Palma shooters were mostly interested in the longer sight radius when using longer barrels. I don't know that shooting a 155 grain bullet at relative higher velocity was effected that much when using a 30 inch barrel.
 

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Barrel length mostly impacts velocity vs true mechanical "accuracy". The case can be made that higher velocity translates to more practical accuracy, but mechanically speaking, there's a little more to it.

What the practical shooter should be concerned with is optimal powder burn, and at 22" on the M14, that's going to be just fine.
 

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I'd like to see some high-speed video of the barrel harmonics on that 88" long tube! I'll bet that it whips around like a wet noodle! The Germans (and probably others) made some cannon tubes so long that they required a trestle to minimize barrel droop. IIRC, the infamous 'Paris Gun' was one such.

Palma shooters at least used to prefer longer than average barrel lengths. Seems like 28-30" were common on those guns. That may have changed in recent years.
The German "Paris-gun" was originally a 211mm bore with a 28 meter barrel, making the barrel approximately 133 calibers long. It was later bored out to 238mm, reducing it to 119 calibers

A 40 inch long .30 barrel is a 133 caliber barrel, , a 35 inch .30 or 19 inch is 118 calibers long.

So, in reality, the Paris-gun was not much longer than current infantry rifles, interior ballistically speaking.

(There was an additional 19 foot long unrifled section added to the muzzle.)
 
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