MV .308 175gr 20" Barrel???


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Eustachius234
August 29, 2009, 07:45 PM
Federal lists their Gold Match 175gr SMK BPHT MV out of a 24" barrel as 2,600fps.

Does anyone know what one can expect the MV of this ammo is out of a 20" barrel?

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Redneck with a 40
August 29, 2009, 11:30 PM
Probably around 2500 fps. Figure 20 fps/inch velocity loss.

Sunray
August 30, 2009, 02:43 AM
"...Figure 20 fps/inch velocity loss..." More like 100 fps. Read a gun rag article long ago where an inch was cut off and shot. Forget the cartridge. Some hunting cartridge. Proved to be about 100 FPS per inch.
The best barrel length for a .308 is 22".

longdayjake
August 30, 2009, 10:44 AM
"...Figure 20 fps/inch velocity loss..." More like 100 fps. Read a gun rag article long ago where an inch was cut off and shot. Forget the cartridge. Some hunting cartridge. Proved to be about 100 FPS per inch.
The best barrel length for a .308 is 22".

If this is the one I am thinking of this test was flawed. They never put a new crown on the gun after cutting down the barrel. That screws up all kinds of things.

freakshow10mm
August 30, 2009, 10:47 AM
Different barrels, bullets, powders will give different results. Shoot over a chrono to know for sure.

Redneck with a 40
August 30, 2009, 10:47 AM
In my Remington 700 SPS Tactical, .308, 20" barrel, I'm getting 2620 fps with my 168 gr handload's, the data on a 24" barrel is 2750 fps. That's right around 30 fps/inch. The .308 is a very efficient cartridge, works good in short barrels.

If you're talking about big magnum's, like a 300 winchester, then you probably will lose 75 fps/inch, you need a long barrel to burn 80 grains of powder.

http://www.chuckhawks.com/rifle_barrel.htm

JDGray
August 30, 2009, 11:19 AM
Every barrel is different, no telling what yours will do. Fed list their 168 GMM load to 2650fps, not sure what barrel length, but my 20" barreled savage 10FP puts them at 2600fps. The "Box" says 2600fps, the web site claims 2650. My barrel is fast compared to some other 20" barrels, just gonna have to chrono yours, to find out;)

rundm
August 30, 2009, 09:13 PM
you will absolutly not lose 100fps. you might lose in the neighborhood of 20-30 fps/in in the 308. In a 300 you would lose quiet a bit more than that. somewhere's around 70-80fps/in.

USSR
August 30, 2009, 09:34 PM
Different barrels, bullets, powders will give different results. Shoot over a chrono to know for sure.

+1. There is no hard-and-fast rule for velocity loss/gain in regards to barrel length. I've got two .30-06 rifles, both with 26" match barrels: with the same load, one does 2875fps and other 2950fps.

Don

taliv
August 30, 2009, 10:45 PM
yep, it's frustrating.

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