how long of a barrel do i need ?

speed demon

Well-Known Member
Oct 4, 2001
how long of a barrel do i need to get all the velocity i can out of a .257 weatherby
mag shooting 85gr or 100 grain bullets..
i know for a fact that it will gain
out to 30 inches.. but how much beyond 30 inches? what gains/speeds with bullet weights did you get darryl with your .25/06?
i have a great deal on a 37 inch barrel in .257 bore.. but i need to know what length to tell the smith to cut it too..
i dont care about the weight.. this gun is
going to be all out for speed.. i dont want to go to far and lose velocity either..
also if any one has any experience with any
other calibers with long barrels... tell me
about it id like to know.. thanks..

Darryl Cassel

Well-Known Member
May 7, 2001

I'm a fan of long barrels and have seen the elevated velocity they produce.

All my rifles are at least 30" and out to 37". Theres NO WAY I could achieve the speed I have from my 338/416 (300 Gr bullets to 3310FPS) unless the barrel was at least 36".

Same with the 30/378 Weatherbys I have had (36") or the 6.5/300 Weatherbys or 7/300 Weatherbys with their 30" tubes.

All of my wife and my 1000 yard guns have 30" barrels on them.

I am ready to go with a 44" tube on a 300 Tomahawk so you see, I like length on barrels.

In ANY caliber you should see a 25 to 35 FPS increase per inch of additional barrel up to a point and that's starting at a 24" to 26". You can never go wrong with at least a 30" barrel.
Again longer is better. I like them 36" and more.

I'm not sure what you would get with the barrel and caliber you mentioned but, I would go with the full length to start with. If it was not satisfactory, you could always have your smith cut it off to a shorter length.

Remember, 100 to 200 FPS additional velocity means alot downrange.

Good Luck to you.


Well-Known Member
Mar 19, 2002
Prince George British Columbia
I been kind of wndering this sort of thing myself. Is there such a thing as length causing to much whip so its not feasable? I know I read some stuff on Lilja's site about a test barrel he was doing and he could actually see the whip. I was thinking of a barrel about 36 to 40" in .338 Lapua 1.25" all the way down and fluted.

speed demon

Well-Known Member
Oct 4, 2001
first.. i want to say THANKS DARRYL you are
the one that started me on long barrels..
its free speed only costing weight in the gun.. i think ill go with a 36 inch one..
and also im going with a 38-40 incher with
my .30-378 when i rebarrel it.. i wanted a
.338/416 but im going to wait as i think
that .408 chevytac may just be the ticket if
sierra comes out with a matchking for it..
i bet a .338/408 with a 40 inch barrel would
be a real speedster too!! i tried to explain
that to some elk/moose hunters about the long range killing power of the .338 300 grain
matchking.. i guess one of these days im going to have to build one and show them..

[ 08-20-2002: Message edited by: speed demon ]


Well-Known Member
Sep 10, 2001
God bless long barrels! As mentioned above you always have the option of cutting it down if deemed appropriate. Advantage gain? How 'bout a 7X57 AI with a 28" Lilja tube that matches the 7mm Rem Mag with 54 gr. of RX19, bullet for bullet.

Another aspect relating to accuracy w/large capacity/small bore/slow powder combos is exit pressure. Short tubes w/ above mentioned circumstances(7 STW for EX) can generate bullet exit pressures in excess of 20kpsi. A) that's wasted velocity, B) it has a rude impact on accuracy. C) what's the point of a slow powder if you're not going to use it? Long is GOOD!

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