F-class shooters, please answer....

[Fatelvis]

I notice a few guys building rifles for F-class competition are using 30" barrels. In the past I wanted 26" barrels on my .308LR rifles, and everyone was telling me that long of a tube was unnecessary, because "powder burn is completed in 22inches" or something to that effect. If that statement was true, WHY would someone go to the extremes, and use a 30"? Thanks-

 

[matt87]

Increased sight radius perhaps, if they are using irons. Also, velocity does not equal accuracy.

 

[USSR]

I notice a few guys building rifles for F-class competition are using 30" barrels. In the past I wanted 26" barrels on my .308LR rifles, and everyone was telling me that long of a tube was unnecessary, because "powder burn is completed in 22inches" or something to that effect. If that statement was true, WHY would someone go to the extremes, and use a 30"?

Fatelvis,

While "powder burn" may be completed in the 22 inches that you mentioned, the pressure created by the burned powder remains and velocity increases even after the powder is consumed. In the case of the .308 at 1k, you need all the velocity you can get, as it is a marginal 1k cartridge at best. Many of the 1k .308 shooters are now shooting the 155gr Lapua Scenar bullet at about 2950fps. That's as good as it gets with a .308.

Don

P.S. - F Class shooters use scopes, so sight radius does not factor in.

 

[Jim Watson]

I have not been in Long Range very long, but the only barrels I have seen as short as 24-26" were the ones on factory rifles being shot at entry level. Like my Savage 12BVSS, bought just before they announced the factory F-class rifles, darn it.

I don't think the statement "powder burn is completed in 22inches" is true. Bullet accleration past about 24" is more gradual than going from short to medium lengths, but it is still there and is "free" with no more powder, pressure, or erosion. And a little more velocity is a little less windage.

A longer barrel also adds weight, which is generally desirable.

 

[Fatelvis]

Thanks for the replies. How much extra velocity could one expect going from a 26" to a 30" barrel?

 

[Jim Watson]

Too many variables to predict. I have seen reports of everything from 8 fps per inch to 25 or more.

When I replaced the factory barrel on that Savage with a Pac-Nor, I bought a 28" largely because that was the longest available at the base price. Longer cost more, so I figured I could get by with 28". It seems to do OK.

 

[USSR]

...I bought a 28" largely because that was the longest available at the base price. Longer cost more, so I figured I could get by with 28".

I did the very same thing when I had my 6.5x55 F Class rifle built. High velocity and weight are your friends in F Class.

Don

 

[Swampy]

While "powder burn" may be completed in the 22 inches that you mentioned, the pressure created by the burned powder remains and velocity increases even after the powder is consumed. In the case of the .308 at 1k, you need all the velocity you can get, as it is a marginal 1k cartridge at best.

+ 1

Best,
Swampy

Garands forever