BullBarrel = Precision or Accuracy?


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ShaiVong
October 30, 2003, 02:26 PM
Let me define the two terms first.

Accuracy is the relative deviation from a "known". I.E. You may have a 3" group at 100 yards, but its centered perfectly on the bullseye.

Precision is repeatability. I.E. you have a 1/4" group, but its 3" to the right of the bullseye.

Ideally you would have a 1/4" group ON the bullseye; thats an accurate and precise rifle.

So this is the question. Do HBAR's give you more precision because they heat more uniformly/less barrel whip and sag? Do they effect your accuracy in the same way?

Say I have two identical rifles; one with a tapered profile barrel, and one with a heavy barrel. Say their both factory. (I think most HBARS are more accurate because they tend to be aftermarket = better qual).

Will the first cold shot of both (assuming they were pre-sighted) be in the bullseye, and will the HBAR pull ahead as followup shots heat the barrel? (assuming they are both freefloated).


I guess what I'm taking forever to ask is: What are the real advantages of a heavy barrel? (besides building muscle to carry :p )

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bogie
October 30, 2003, 02:52 PM
Less barrel whip. Light Varmint and Heavy Varmint barrels are tapered, but they're not tapered a lot. A large effective cross section helps stop the whip.

Longer barrels whip more.

Zak Smith
October 30, 2003, 03:22 PM
More rifle mass will reduce the rifle's movement due to your body vibrations.

-z

critter
October 30, 2003, 03:29 PM
I think the answer to your question is that they are SUPPOSED to do both. That is, as they heat up, the group size will:
(1) INCREASE LESS than a smaller barrel, AND
(2) the point of impact should also remain consistant with that from the cold barrel.

Now, whether or not they actually do both of those will probably depend on the individual barrels in question, but your chances of having both happen should be greater with the heavier barrel.

Art Eatman
October 30, 2003, 06:08 PM
The heavy barrel provides more of a heat sink, so a longer string of shots won't raise its temperature as much as for a thin barrel. This tends to reduce the amount of stress caused by heat. The result, then, is more uniformity from shot to shot.

The larger surface area allows a more rapid cooling, as well.

If a particular load is tailored to the harmonics of the barrel, the importance of stiffness--and therefore length--is reduced. (This in essence is the reverse of what you do with the Browning BOSS system, where you tailor the harmonics to the load.)

Art

Nando Aqui
October 30, 2003, 06:42 PM
The heavy barrel provides more of a heat sink, so a longer string of shots won't raise its temperature as much as for a thin barrel. This tends to reduce the amount of stress caused by heat. The result, then, is more uniformity from shot to shot.

The larger surface area allows a more rapid cooling, as well. True, it will stay cooler longer, but that is because it has greater mass and will require more heat to raise its temperature. BUT, by the same token, it will stay hotter longer for the same reason.

[Easy visualization: Use a torch to heat up a 1/4" steel rod red hot and see how long it takes. Then try the same thing but with a 2" rod. It will take a lot longer to do the 2" rod. Then, dunk them in water (no, don't do it) and see how much more water the 2" rod evaporates than the 1/4". And if you leave them alone to cool off in air, the 1/4" will cool off a lot faster.]


Alex

Jim K
October 30, 2003, 09:04 PM
I agree in general that heavy barrels will be more accurate, for the reasons given. But one of the most accurate barrels I ever saw was a .308 barrel on a Mauser VZ-24 receiver. That barrel measured under 1/2 inch at the muzzle, but shot less than 1/2 inch groups (with the right ammo) and would do it about all day. Sometimes stuff just refuses to go by the rules.

Jim

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