Max barrel length for 338 Lapua and 300RUM

[tunofun]

GDay fellas, I have been doing a bit of research lately to rebarrel my .308 to a .284WIN and was talking to a guy here down under that can make a barrel for me in ANY length I want. I want a 28" for the .284 but later on I want to build either a .300RUM or .338 Lapua and was thinking what length barrel would you choose if there were no limitations?
He can do any rifled calibre from .08 (I know!) to .458, any shotgun size and any length up to 120 inches. I know it sounds absurd but an old guy I know had a 1 bore shotgun years ago and this guy made him a 96" barrel for it. I also heard of this guy making a 52" barrel for a .17/22-243 Middelstead Wildcat that was spitting a 30gr projectile out at 5300fps!

Don't worry about weight or ability to move it around, just what length would you have if you could have any length?

 

[Ballistic64]

Sorry I'm off topic from your question,but I just have to ask.Werent guns made illegal in Australia?

 

[tunofun]

Ahhhh, no, semi-auto rifles/shotguns and pump action shotguns were made illegal in 1997 after the government decided we didn't need them. Fuckwits.

 

[Ballistic64]

Yeah,weve got our fair share here too.
Not sure what the diminishing return would be on barrel length.I opted for a 30" tube on the Lapua I'm building.I read in Liljas site that Dan had a 42" tube on one.It would be interesting to have a long barrel and gradually have it shortened to see the results.

 

[1doug]

It seems like dan @ lilja had done the exact same thing you mentioned.

 

[Fiftydriver]

Tunofun,

If you go to Dan Lilja web site he has all these ariticles for you to read. Good stuff.

Go to:

www.riflebarrels.com

TO be honest, in a 338 bore with the case capacity of the Lapua, I would not recommend anything over 34". The reason is that at this length you will only be gaining around 10 to 12 fps per additional inch of barrel.

The disadvantage is that past 34", barrel whip becomes more of a problem and will detract from accuracy.

The 300 RUM would be similar but I would say 36" would be about what I would consider max. The basic same case capacity with the smaller bore will increase fps per inch of barrel length but only to around 15 fps at this length. The added velocity is not worth the decreasing rigidity of the lengthening barrel.

That said, if you used a 2" diameter barrel you could probably reach out 50" pretty easily but ballistically, you would not gain as much as most think.

Good Shooting!!

Kirby Allen(50)

 

[tunofun]

Hey, thanks for the input guys, fifty driver, that was the answer I was after! Cheers!
I had heard that dan @ lilja made a simlar .17 barrel to the one i described but it was made from welding two 27" barrels together using a projectile to line up the rifling. I believe.

 

[ricka0]

Differential Velocity gain
Data From Daniel Lilja, shows diminishing returns. Dan said he would send me the code he wrote to generate the data so I could go shorter than 28" (as a lot of 50 folks are going much shorter)

As you can see, once you get out to 40" you only gain 10 FPS with each addition inch.

Lilja on barrel len vs vel

 

[brian b]

I have a 338 Lapua Imp. with a 36" barrel and the only real advantage is that I can set the barrel back a few inch's after a 1000 rounds and not give up that much velocity, not worried too much with barrel whip 1.45" with barrel block.
B