Fluting a barrel after its been shot and broke in is not the best idea especialy if its a factory forged barrel or a button rifled , its still not a good idea to flute a cut rifled barrel after its been finish lapped unless you making very shallow flutes which is not gonna give you any weight reduction to speak of.
When button rifled or forge rifled barrel are made they use a tremondus amout of pressure to either beat the barrel down into the mandrel that has lands on it to make the grooves or they push or pull a carbide button through the bore and that basical "irons" the lands and grooves into place , both of these processes put a great deal of stress into the barrel and if you go removing metal from it the barrel will move around and if the bore happens to open up even a couple tenths (.0002) the barrel will likely be a poor shooter. Companies that make barrels this way , flute their barrel , after they are bored and rifled but before they are finish lapped , the final lapping after the fluting will bring the bore dementions back into the same plane if the bore has moved.
Barrels that are cut rifled like Rock Creek , Kreiger , Bartlein , and a few others use a single point broach that removes the material where the grooves are gonna be this process doens not induce any stress into the barrel their for they are far less likely to "move" during fluting , BUT , as far as I know they still lap their barrels after they are fluted. I talked to Mike Rock about how he flutes his barrels so deep with such huge flutes to get maximum weight reduction and he told me that he drilles the barrel out , flutes it then goes through the rifleing process this insures that the lands and grooves would have any added stress to deal with after they are made ,if this is truely the way its done their I believe this is the best method I've heard of , I have one of his heavly fluted barrels on a tactical 308 and it shoots as well as any other gun I've seen built with a Rock barrel (awsome)
Its commonly said that a fluted barrel is more stiff than a none fluted barrel this is both true and false. A barrel that is 26" long , weighs 5lbs and is fluted will definatly be stiffer than a none fluted barrel thats 26" long and weighs 5lbs , this is because the fluted barrel will be larger in diameter and the fatter a barrel is the stiffer it is.
Now if you take a #8 conture barrel thats 26" long and fluted then compair it to a barrel that is the exact same conture but not fluted the non fluted barrel will be stiffer every time , its impossible to remove material from a cylinder (other than making it shorter) and have it more stiff than it was before.
Back to your question , you can roll the dice and take a chance that your barrel will shoot as well as it does now after its fluted but if it doesen't you just wasted $100-$150. I personaly would not risk it. Some guys can flute a bigger barrel like a #7 and remove as much as a pound and thats alot , if a guy were to come to me and ask me to make his gun lighter the barrel would be the last thing I'd mess with and when it came time to cut weight their I cut off 2" of the muzzle , you will likely loose more weight AND the gun will probably shoot better , because the shorter barrel will be stiffer and probably have a better crown , yes with some rounds their might be as much as a 150fps loss in velocity but this is generaly only with the big over bore mags like the 300RUM but I seriously doubt that any animal would be able to tell that the speed had dropped a little.
Sorry for being so long winded but I just wanted to give a full explanation for why I thought it was a bad idea
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