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Is my barrel to long?

 
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  #1  
Old 10-05-2012, 10:09 PM
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Is my barrel to long?

Having a custom 338AI built. I read here that someone did a test starting with a 36" and cut 1" off at a time. Anyting shorter that 34" he lost 150fps per 1" cut off.
Am I going to have accuracy issues (barrel harmonics)?because of the length 34"?
Not shure of the taper but the barrel will weigh about 8lbs.

I have talked to locals that had 34" barrels lighter barrels and had to cut them down to 30" because of barrel harmonics.
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  #2  
Old 10-06-2012, 07:55 AM
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Re: Is my barrel to long?

Dan Lilja ran a similar test, it should be close enough to what you have to give you an idea what happens and why

Lilja Precision Rifle Barrels - Articles: Barrel Lenghts and Velocities in the 338/378 Weatherby Magnum
__________________
Keep in mind the animals we shoot for food and display are not bullet proof. Contrary to popular belief, they bleed and die just like they did a hundred years ago. Being competent with a given rifle is far more important than impressive ballistics and poor shootability. High velocity misses never put a steak in the freezer.

Joe
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  #3  
Old 10-06-2012, 01:08 PM
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Re: Is my barrel to long?

Quote:
Originally Posted by Joe King View Post
Dan Lilja ran a similar test, it should be close enough to what you have to give you an idea what happens and why

Lilja Precision Rifle Barrels - Articles: Barrel Lenghts and Velocities in the 338/378 Weatherby Magnum
a true .338AI is based off the 30-06 case, and anything longer than 26" is a complete waste of steel. He never messed with the 378 series case.
gary
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  #4  
Old 10-06-2012, 02:38 PM
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Re: Is my barrel to long?

What 338 are we talkin about?

You might notice with Dan's charts that velocity nodes appear through the range of both 250/300gr bullets. If he had started beyond 46" he would have seen velocity rise continue with the 250gr -beyond 46". I think with a strain gauge he would have seen shockwave pressure peaks/toughs at cycles down the bore. And this would have been different with another powder.
His 338/378wm would be ~50gr larger than an improved 338-06.

Personally, I believe the right barrel length brings a balance between powder burn & tuning quality.
Too short of a barrel causes ugly bullet release due to high muzzle pressures. This would show up with distance shooting. Too long of a barrel could screw up the chances of reaching good performance, as well as lower probability of first shot accuracy. Trying to counter this with a heavier barrel, means accepting an even heavier gun to produce a gun balance that behaves.

If I were building a 338 whatever, I'd find(via internet search) a recipe that happened to work for more than one shooter, and not 'tactical' shooters. Look for shooting at ~1/2moa targets at a mid-ranges like 600-800yds, rather than someone walking shots into 5moa steel a mile away..
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  #5  
Old 10-06-2012, 03:42 PM
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Re: Is my barrel to long?

Quote:
Originally Posted by Trickymissfit View Post
a true .338AI is based off the 30-06 case, and anything longer than 26" is a complete waste of steel. He never messed with the 378 series case.
gary
I was referring to his findings related to barrel length only. I do not see what case capacity has to with anything beyond what MikeCR stated. Which I completely agree with

Quote:
Personally, I believe the right barrel length brings a balance between powder burn & tuning quality.
Too short of a barrel causes ugly bullet release due to high muzzle pressures. This would show up with distance shooting. Too long of a barrel could screw up the chances of reaching good performance, as well as lower probability of first shot accuracy. Trying to counter this with a heavier barrel, means accepting an even heavier gun to produce a gun balance that behaves.

are you saying Dan Lilja never messed with 378 based chamberings? Cause he used a 338-378 for that test
__________________
Keep in mind the animals we shoot for food and display are not bullet proof. Contrary to popular belief, they bleed and die just like they did a hundred years ago. Being competent with a given rifle is far more important than impressive ballistics and poor shootability. High velocity misses never put a steak in the freezer.

Joe
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  #6  
Old 10-06-2012, 06:29 PM
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Join Date: Aug 2003
Location: NC, oceanfront
Posts: 3,221
Re: Is my barrel to long?

Quote:
Originally Posted by Joe King View Post
are you saying Dan Lilja never messed with 378 based chamberings? Cause he used a 338-378 for that test
No, I'm sure Dan knew just what he was doing. His test was an exploration, with his conclusion being:
---------------------------------------------------------------------------------------------------------------------
For lighter weight, walk-around-type hunting rifles chambered for big cartridges like the 338/378 Weatherby magnum, extra- long barrels are not going to gain any significant velocity increases. As I found out too, long skinny barrels are whippy, especially with the high recoil cartridges and loads. My recommendation is to use no longer than a 30" barrel with a minimum barrel contour of a #4. A better choice would be a fluted #5 or #6 contour. Barrels over 30" are going to have to be heavier to counter the "fly rod-phenonomen" and will probably be too heavy for most walk-around-type rifles. Or rather, too heavy for the gun bearers.
---------------------------------------------------------------------------------------------------------------------
30" & 7-8 pound barrel. Sounds rational to me.
But then, this test did not include accuracy or precision in barrel choice. He implied those factors, which probably represents his experience with the cartridge.
I'm also referring to a balance, that includes accuracy and field functioning.

But we don't know for sure yet what fastfire57's 338AI is going to be
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  #7  
Old 10-06-2012, 06:32 PM
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Join Date: Feb 2012
Posts: 46
Re: Is my barrel to long?

338 Lapua




Quote:
Originally Posted by Mikecr View Post
What 338 are we talkin about?

You might notice with Dan's charts that velocity nodes appear through the range of both 250/300gr bullets. If he had started beyond 46" he would have seen velocity rise continue with the 250gr -beyond 46". I think with a strain gauge he would have seen shockwave pressure peaks/toughs at cycles down the bore. And this would have been different with another powder.
His 338/378wm would be ~50gr larger than an improved 338-06.

Personally, I believe the right barrel length brings a balance between powder burn & tuning quality.
Too short of a barrel causes ugly bullet release due to high muzzle pressures. This would show up with distance shooting. Too long of a barrel could screw up the chances of reaching good performance, as well as lower probability of first shot accuracy. Trying to counter this with a heavier barrel, means accepting an even heavier gun to produce a gun balance that behaves.

If I were building a 338 whatever, I'd find(via internet search) a recipe that happened to work for more than one shooter, and not 'tactical' shooters. Look for shooting at ~1/2moa targets at a mid-ranges like 600-800yds, rather than someone walking shots into 5moa steel a mile away..
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