Fluted Barrels

[Captcurt]

The thread on barrel harmonics got me to thinking. I have always wondered about the accuracy of fluted barrels as they heat. I realize that it saves weight and probably doesn't have much effect with casual shooting or hunting where few rapid shots are fired. But what about a long term bench session. It would appear that the flutes could cause the barrel to heat unevenly and cause the POI to change. Has anyone tested this theory? Inquiring minds need to know.

 

[Varminterror]

This is far and away the deepest fluting, tightest spiral, lightest contour fluted barrel I have owned, and which I put through both the most scrutinizing analysis and most abuse. This barrel would get EXCEPTIONALLY hot during matches, to the point it once literally burned my skin to the point of scabbing after incidental contact on my neck. But the POI held true.

The smallest shooting barrels in the world aren’t fluted, but not necessarily for any effect of the fluting itself - it simply costs more and reduces weight and stiffness, all of which are contraindicated for competition shooting.

In principle, the flutes should be symmetrical around the bore, so expansion will also be symmetrical. Maybe not as radially uniform as an annular cross-section of a conventional contour, but on a net basis, still radially uniform. Spiral fluting, naturally, would SEEM to be a deviation from this, but overall, the cross-sections remain symmetrical, so the expansion and internal forces aren’t uneven.

Overall, fluting a barrel - properly - won’t cause a barrel to walk any more than a normal barrel, and a guy can shoot bugholes with any of them - but if you’re competing where hundredths count, fluting is moot, and simply isn’t part of the vocabulary.

 

[lightman]

I have a few fluted barrels but have not done any testing or comparisons. I sprung for the fluted barrels just because I think they look sexy! Mine have straight flutes and a mix of the Remington size flutes and the Krieger flutes.

 

[JFrank]

They reduce weight but from what I’ve seen heat and cool unevenly.

 

[mcb]

Flutes reduce weight, increase area for cooling, while being stiffer than round barrel of the same cross sectional area.

The ability of any barrel to maintain POI as it heats required very good symmetry about the bores axis, of the actual geometry, and equally important the residual stress levels from the manufacturing and heat treating process.

Round is easy to machine symmetric, flutes are harder to maintain the symmetry but still well within the machining tolerance of a high quality barrel maker.

All the recent US military sniper rifles use fluted barrels.
M2010, a 700 Long action in 300 WM in a RACS chassis
PSR, Remington change barrel sniper rifle system (7.62 NATA, 300 WM, 338 LM) on a RACS chassis
ASR (Beretta's MRAD change barrel sniper rifle system that replaced the PSR (7.62 NATO, 300 NM, 338 NM)