This is a rec.guns post that I formatted for the web.
# I seen a thread that says factory/production fluting may be unreliable, that #is not always done right and to stay away from it.
This is a controversial topic. I'll try to sum-up fairly, but I'll get flamed anyway.
1. The best argument for a fluted barrel is that it weighs less than a barrel of the same profile, without sacrificing much stiffness. (An argument cannot be made that a fluted barrel is STIFFER than a heavier round barrel of the same size, as removing steel never made a cylinder stronger. As for the argument that the fluted barrel is "stiffer" than a thinner barrel of the same weight, see below.)
2. The second best argument is that fluting makes a rifle lighter without a noticable, or only a negligible, decrease in accuracy.
3. The third best argument is that it cools faster. However, a heavier barrel also heats-up slower, so that's your tradeoff.
4. It looks cool.
Arguments against fluting:
1. Fluting moves primary vibratory motion into more complex secondary, tertiary etc. forms of harmonic motion. This is because the fluted barrel is more likely to flex where it is not reinforced. Putting an odd number of flutes on it just increases the complexity of the harmonics.
Since compensating for primary vibration is just a matter of finding a happy node and sticking with it by loading to a certain velocity (found by experimentation), it is the other harmonics that are the primary cause of natural inaccuracy in an otherwise sound gun. This is covered in detail in Harold Vaughn's recent tome, and I defer discussion to that authority.
Referring back to Argument #1 FOR fluting, a thinner non-fluted barrel of the same weight may have more primary harmonic motion. But, we know how to compensate for that. It will probably have less secondary, tert. etc. motion, as there is no assymetry in it to promote it. This means that the thinner barrel can be load-compensated by loading to specific velocities, and accuracy can be achieved.
It may, however, have relatively few velocities where it is highly accurate, compared to a thicker barrel with slower primary harmonics. This is why thinner barrels "like" fewer loads than thick barrels.
A thicker fluted barrel, having less barrel whip in the primary harmonic, will shoot various loads to a smaller extreme spread of dispersion. It will however, be more difficult to find loads that have a greater precision accuracy, as loads that compensate for primary and secondary harmonics will encounter greater and more complex tertiary and quaternary harmonics, loads that compensate for primary and tertiary harmonics will encounter greater secondary harmonics, etc.
So, we would find that a fluted heavy barrel may shoot OK with most any load, but not fantastic with any one load.
2. If done improperly or the barrel is stressed by the operation, fluting can cause uneven expansion when heated, increasing dispersion when hot and therefore decreasing accuracy.
3. Engineers may laugh at you and then lead you through embarrasing "thought experiments" that lead you to question your choice in barrels.
Ken.
PS My thanks to the structural engineer on this newsgroup who lead me through some thought experiments a few years ago. :)
Note: Since I wrote this, I found this post by a noted barrel and rifle maker: Gale McM. on fluting.
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