Barrel Length vs Veleocity

Ganderite

Ganderite

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Farm south of North Bay
Summary: In 308Win you lose about 25 fps per inch cut off.



http://www.thefirearmblog.com/blog/2015/02/04/rifleshooter-coms-barrel-length-velocity-tests/?utm_source=Newsletter&utm_medium=Email&utm_content=2015-02-10&utm_campaign=Weekly+Newsletter

I recall taking a used 30" target barrel and cutting it back to 20" for a project. We used a hacksaw in the back yard and cut it off in 1" pieces and Chronied it all the way. The average was about 30 fps per inch - similar to the published report. I was surprised at how small the velocity loss was.
 
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Not as much as some people think and for most purposes the velocity loss or gain can be ignored. Long range target shooting is another matter.
 
At a shooting match there was an interesting array of AR-15 type rifles. One with a 7 inch barrel as well as the usual assortment of 10.5, 14.5 and 20 inch barrels. We were curious to know what the velocities would be. We fired 5 rounds from each barrel length. We used standard IVI military type ammo in all rifles with the following results:
• 20 inch barrel – 3094 fps

• 14.5 inch barrel – 2858 fps - 43 fps/inch

• 10.5 inch barrel – 2562 fps - 74 fps/inch

• 7 inch barrel – 2219 fps - 98 fps/inch
 
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Ganderite said:
At a shooting match there was an interesting array of rifles. One with a 7 inch barrel as well as the usual assortment of 10.5, 14.5 and 20 inch barrels. We were curious to know what the velocities would be. We fired 5 rounds from each barrel length. We used standard IVI military type ammo in all rifles with the following results:
• 20 inch barrel – 3094 fps
• 14.5 inch barrel – 2858 fps
• 10.5 inch barrel – 2562 fps
• 7 inch barrel – 2219 fps
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That is definitely good to know. It's nice to know what the difference is for the shorter barrels.
 
From the linked article:

308 Winchester Barrel length in inches versus Muzzle velocity in feet-per-second (ft/sec)Rifleshooter.com
Barrel length Winchester 147 FMJ IMI Samson 7.62 150 FMJ Federal 168 Gold Medal Winchester 180 PP
  • 28" 2965 2823 2706 2632
  • 27" 2962 2800 2697 2607
  • 26" 2955 2801 2673 2597
  • 25" 2917 2769 2659 2585
  • 24" 2909 2766 2635 2553
  • 23" 2877 2744 2618 2553
  • 22" 2837 2718 2597 2527
  • 21" 2807 2683 2580 2507
  • 20" 2804 2679 2565 2478
  • 19" 2757 2634 2532 2441
  • 18" 2739 2595 2523 2411
  • 17" 2707 2577 2481 2401
  • 16.5" 2682 2561 2466 2373

AVG velocity loss fps/inch 24.6 22.8 20.9 22.5
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The average belies certain details. too me, this makes it look like 26inches is a bit of a sweet spot... Longer than that, the gains are minimal, shorter than that, you start to see drops of a more significant nature.

But man, a 26" BBL .308, that would be a bit of a pole vaulting stick.

20" seems like it might be another sweet spot....
 
grelmar said:
From the linked article:



The average belies certain details. too me, this makes it look like 26inches is a bit of a sweet spot... Longer than that, the gains are minimal, shorter than that, you start to see drops of a more significant nature.

But man, a 26" BBL .308, that would be a bit of a pole vaulting stick.

20" seems like it might be another sweet spot....
Click to expand...

Sweet spot is likely 25 3/16".
 
Ganderite said:
The fireball and bark with some ammo is very impressive. In fact, it is so bad that I would say the gun is useless as a weapon, especially indoors, unless it was practical for the shooter to be using good hearing protection.
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Being the guy standing next to this person at the range, I wouldn't be impressed at all.
 
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People seem to get too much in love with Velocity. "Gotta have the fastest rifle in the calibre."

On target ranges, the biggest advantage to the longer barrels is the distance between the sights. For hunting, it it another matter. After hunting all over Canada for 60 plus years, I have found that a well balanced, shorter barreled rifle of an adequate calibre is a lot more usefull than a longer and heavier barreled one.

Actually, my "go to" rifle is an older Ruger .308 Carbine, full stocked with a barrel slightly over 18 inches long. It delivers a 165 grain bullet where it needs to, and a LOT of big game has fallen in front of it.

My criteria is ACCURACY and not VELOCITY. It is no good having something going like a bat out of hell if you can not hit anything with it.
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My Test load for .303 chronos 2250 ft/sec in an SMLE, which has a 25.4-inch barrel.

Same ammo, same day, chronoed 2380 out of a full length Ross with a 30.2-inch barrel.

That is 130 ft/sec difference for 5.8 inches of tube.

Call it roughly 25 ft/sec and you're close.
 
Found this table:

velocityvbrllngth.jpg
 
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