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Real difference...in barrels..

 
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  #1  
Old 03-07-2008, 01:55 AM
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Real difference...in barrels..

next project, a light well mannered rifle...

is there a real difference in accuracy between diferent barrel contours of the same brand?

a contour 1 VS a contour 5 VS a contour 7?

I know the about the advantage of the barrel weght, but what about accuracy?

in less kicking rifles(i.e a 22-250), is a contour 1 is more accurate than a contour 5? if yes, why? if the contour 5 is more accurate, why?

how about, is a light contour more finicky to reload than a heavy contour?

sorry about so many questions..



Joe
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  #2  
Old 03-07-2008, 02:39 AM
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Barrel stiffness is the governing factor in accuracy.You don't see too many 'soda straw' barrels on benchrest lines for a reason.Barrel weight in heavy contours is easily managed these days by putting flutes on them.The good thing about fluting is that the barrel has the same amount of stiffness,but is lighter,and it helps cool things down a little faster by having more surface area.
The difference in accuracy comes from the fact that a stiffer barrel whips less,and by tuning your loads to have a barrel time that coincides with the 'whip' to have the bullet exit at that point in the 'whip' when it is stationary.
Light recoil or heavy recoil have no bearing on accuracy,so a no.1 contour is not going to make a difference on a 22-250 over a no.5 contour,both can be as accurate as the other.How these barrels are bedded makes a significant difference.Fore end pressure on a light barrel will distort it more,than the same amount of pressure on a heavier,stiffer barrel ,once the two heat up.
Also barrel length has no bearing on accuracy,so any length,contour and fluting can be used for whatever calibre the rifle may be.
Lastly, a light contour barrel can be finnicky to handload for,for the reasons I've already stated above,but that said,there is no reason for a light barrel to be anymore finnicky than a heavy barrel.All barrels can be finnicky if they have an unforeseen tight spot or damage internally,because this will change barrel time on every consecutive shot,as more fouling builds on that spot.
It is not an exact science,many have tried to come up with the answer "why some barrels shoot better than others'.
Hope this helps.
MagnumManiac
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Old 03-07-2008, 11:07 AM
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Quote:
Originally Posted by MagnumManiac View Post

Barrel stiffness is the governing factor in accuracy.

The difference in accuracy comes from the fact that a stiffer barrel whips less,and by tuning your loads to have a barrel time that coincides with the 'whip' to have the bullet exit at that point in the 'whip' when it is stationary.

Also barrel length has no bearing on accuracy,so any length,contour and fluting can be used for whatever calibre the rifle may be.
MagnumManiac

You are contradicting yourself!

*If*, as you claim, "Barrel stiffness is the governing factor in accuracy." (I don't believe that for a second!)........then shorter barrels would always be more accurate than longer barrels (of the same contour) because shorter barrels are ALWAYS stiffer than longer barrels of the same contour........
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Old 03-07-2008, 12:28 PM
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The BR boys as well as other target and tactical shooters use heavy barrels because they hold accuracy for more shots because they don't heat up as fast , you can have a 338 with a #1 conture shoot just as accurate as a 338 with a #8 conture as long as its well made and properly installed. NOW , it won't shoot as tight of groups in the 5-10 shot range than the heavier barrel because after 3 rounds its gonna be hot and when steel gets hot it moves.

People think that shorter barrels are more accurate than long barrel because a 18" barrle that 1.25" in diameter is alot stiffer than a 28" barrel in the same diameter but if you had a 30" long 3" diameter barrel it would be stiffer than a 18" 1.25" tube.

I once owned a very thin (.480" at the muzzel) barreled 300 Wby mag and it would shoot 3 shot groups in the .5" range consistantly if you gave it a couple minutes between shots. So yes a very light rifle can be made to shoot very accuratly.

To say that recoil has no bearing on accuracy is a very bold statement , recoil is directly linked to accuracy because if a gun knocks the hell out of you everytime your pull the trigger your not gonna shoot it as well , this is why guys put brake on big rifles that they plan to shoot more than once a day and expect fine accuracy from. Now to say that the differance in recoil between a 6lb , 22-250 and a 12lb , 22-250 is enough to affect accuracy , well that depends on the shooter , the lighter gun will certainly kick more but not enought to cause any sort of flintch at least not for me , but some folks a little bit of recoil goes a long way.

If you flute a thinner sporter barrel for the sake of reducing weight your going in the wrong direction as the flutes are so shallow that the amout of weight lost could easly have been reduced with differant scope rings and bases.
If you have two barrels , say #7 conture and then both weigh 6lbs , you take one and flute the hell out of it you may be able to drop a little more than a pound. Now that #7 conture fluted barrel is not going to be nearly as stiff as the solid #7 but it will be stiffer than a #5 conture. so the differance in weight is up to you in the end but I assure you that in a mild kicking caliber that a thin barrel can be made to shoot as well as a heavy barrel thoug it wount shoot as well for as long
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  #5  
Old 03-07-2008, 12:32 PM
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Joe,

On average, the lighter the contour of the barrel, the shorter you want to limits overall length to retain as much barrel stiffness as possible. For example, if you take a lilja #3 contour and have it in a 30" length chambered in say 7mm WSM and then take the same contour barrel and fit it to an XP-100 handgun with a 15" barrel length. In most every case, I would bet the handgun would far out shoot the 30" barrel as far as shear group size.

That said, how much difference would there be with same length barrel stepping up or down in barrel contour, in my opinion, not a hell of a lot if the barrel is a good one and the work on the barrel is properly done.

What you will find and this is why most believe that lighter contour barrels are not as accurate as heavier contour is simply because a lighter rifle is more difficult to shoot accurately then a heavier rifle.

It just takes more of a pilot to shoot a light weight rifle compared to one that will sit there basically on its own.

That said, it also depends on barrel length, chambering, stock choices, twist rate, bullet length and velocity potential. The farther to the extreme you get in performance, the more stress there is imposed on the entire rifle project.

For example, you take a 200 gr ULD RBBT 7mm bullet and load it to 3350 fps and compare it to a 160 gr Accubond loaded to 3000 fps, the former bullet will impose dramatically more stress on any barrel when it passes down the bore, as such, a larger cross section barrel will always help control this better then a smaller contour barrel.

Kirby Allen(50)
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Old 03-08-2008, 10:51 AM
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For cold bore single shot ACCURACY(which should be what this site is about) contour makes absolutely no difference.
Just get a contour that will balance well in a carry rifle.

The biggest factor here is whether the barrel maker actually knows how to make accurate barrels -in lighter contours. This comes down to controlling muzzle growth as part of their process. Most do not. They get hung up in the benchrest mindsets, and sales -like we do. BR barrels are easiest to make and are most likely to shoot well(for BR competition). So many, many barrel makers prefer only BR barrels, and have no accounting of muzzle growth. They don't even measure it.

I prefer cut rifled, especially with heavily turned barrels because I assume up front, that the barrel maker does not measure and control bore growth, and cut rifling produces least stress.
But the best(for light, accurate barrels) may actually be hammer forged. This because their bores shrink with contouring. These would not be worth a damn for BR shooting though, as many have found.

I guess what I'm saying is that contour itself is not a factor for accuracy. But's it's manufactoring may be.
See if you can get a barrelmaker to discuss his method of controlling bore growth with contouring. Ask him how he measures it.
I think you'll find that he generalizes it(blows it off), side steps into a brag of end to end consistancy as 'compared'(not measured) by an air gauge. Or he'll offer you a fine bull barrel, and a few boasts of winning BR history.
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  #7  
Old 03-09-2008, 12:46 AM
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thanks to you all...

I`m a gunsmith down in Mexico and usually do this type of work only on my own rifles, but opinions from you folks is respected, as I understand that only accurate guns are worth having.


I asked this questions because many of you work on guns and because you work on so many guns...many times the number I do at my shop.

my experience building rifles is not as extensive as yours. but I`m still learning.

thanks.
Joe
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