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Old September 22, 2006, 04:30 PM   #1
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Those w/ Chrono's general question

For you guys who have a chrono, what have you found IN GENERAL the reduction in velocity from a 24" barrel to a 22" barrel? And vice Versa, the increase from a 24" to a 26"?

specifically, to any of these calibers: 22-250, 270, 7mm rem mag, 300 win mag.
I was just curious...yes, I know the golden answer...It depends. So humor me and get me a general answer...
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Old September 22, 2006, 05:03 PM   #2
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I've never made that type of comparison. To do so I would have to own two rifles of the same type and caliber and shoot exactly the same loads in each. I can tell you that looking back over load data I have kept over the years, that my 26" .223 varmint class shoots a load somewhat faster than the 18- 1/2" barrel on a mini-14. I don't really keep track of load data for the mini-14 anymore as I shoot the rejects that ended up in the plinker drawer in it. The last load I have data for in both rifles showed about a 150 fps difference in the average velocity.
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Old September 22, 2006, 11:02 PM   #3
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Chrono's and barrel inches.

Using my Pact proof channel chrono, I went out to prove to myself that a longer barrel gave more velocity, and a shorter one less. After much trial and tribulation, that is not what I have found.

Shorter barrels generally give you a loss of a few fps for each inch it is shorter, except in one case I tried 2 Remington 700 bolt action rifles in 308 win, one with a 20 inch barrel, and one with a 22 inch barrel. For some reason the 20 inch barrel shot as fast as the 22 inch barrel, same load was used in each gun.

Much the same result with two Savage bolt actions in 22-250. Same load was used in each gun. The 22 inch barrel gave slightly more velocity than the 20 inch barrel, but later the 20 inch barrel came within 8fps of matching the muzzle velocity of the 22 inch barrel.

So basically you can say a longer barrel should give you more velocity, but a shorter barrel may not cause you to lose any. [] Perhaps with these more modern powder choices, any non magnum cartridge can attain maximum velocity in as little as 16 or 18 inches.
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Old September 23, 2006, 03:19 AM   #4
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The length of the barrel is one factor in velocity. For any modern caliber in less that a 30" barrel, shorter barrels will yeild less velocity. Some loadings like 22lr don't see much advantage past a certain length.

If you have two rifles chambered to fire the same round with a 20" and a 22" and you are getting the same velocity, then there are other differences as well (chamber dimensions, rifling, smoothness of the lands, etc). If you cut a barrrel down by 2" and fire the same loadings, you will get less velocity.


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Old September 23, 2006, 08:54 AM   #5
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223 in progressively shorter barrels was done and is posted here.
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Old September 24, 2006, 10:13 AM   #6
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THANKS all. REM, that was great data. The velocity loss was significantly less than what I was told to expect, and explains why my loads I test fired off a friends chrono yielded a much higher velocity than I was expecting. I was told from a guy (whom I don't know) to expect about 150 fps for 2" less. That obviously is not the case. Thanks for the info guys.
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