Fluting a barrels thats allready been shot

[James Jones]

I was wondering if any of you guys have ever had a button rifled barrel fluted after it has been finished ie lapped and shot.
did it have any effects on accuracy? how big and deep were the flutes?

I've got a Pac-Nor I'm thinking about having done

 

[Bart B]

I know a few folks who have air gaged button rifled barrels (Hart, Douglass, Shilen, Schneider, others) before and after fluting them. They all have observed the same stuff. Before fluting, the groove diameters are very uniform.

After fluting about 3/16th inch wide and deep, the groove diameters are smaller starting into the fluted area then open up to a larger diameter than before fluting under the flutes, then go back to less than original groove diameter a bit. Quite a ways from the flutes, groove diameter stays the same.

Accuracy has always been worse after fluting. Well, the bore dimensions went haywire so it's no wonder accuracy went to pot.

And the barrel is always less stiff after fluting than before; you've removed part of the metal that made it as stiff as it was.

 

[BountyHunter]

Most mftrs will have you flute the barrel before final lapping or at least after fluting send it back for relapping. I know that Broughton (Tim North) for example has it done that way and says he can feel the difference when relapping a fluted barrel.

also fluting makes a barrel stiffer "per weight" than an unfluted barrel of the same weight. That is often a confusing point.

Many people do it to add "cooling" but sand blasting the barrel is better and cheaper for cooling purposes.

BH

 

[koginam]

I have two barrels that were fluted after being shot for a few hundred rounds. I don't know if it was because they were fluted on a vertical mill which puts no downward pressure on the barrel, instead of a horizontal mill which puts extreme downward pressure on the barrel but there was little difference in how they shot afterward.