On Monday 17 July 2017 11:08:19 andy pugh wrote: > On 17 July 2017 at 15:42, Gene Heskett <ghesk...@shentel.net> wrote: > > I saw that, and the long pipe gripped in the chuck with the huge > > bearing so it all turned. The bearing is nice but $$$$$$ and not > > needed if the tube is turned truly round. > > I imagine that a suitable bearing could be found that would not be all > that expensive, especially as you could make the tool to suit the > available bearing. > http://www.ebay.com/itm/280920636178 looks like it could work. > > And I seem to recall that rifle barrels are very rarely circular. > (though in the case of that rig in the video the real problem would be > the gun carriage trunnions)
In the case of a bolt action hunting rifle, that stuff is on the action, barrels are generally turned smooth. Any taper is optional, this one tapers to .82" at the muzzle. The only place where the installed barrels rotation is important is a flat just wide enough to clear the claw style extractor when the bolt is closed. Its often filed by hand after the barrel is screwed in and an impression made in some modeling clay to mark the boundaries by the bolt, with extractor mounted, being pushed into the clay. Or a witness mark made on the bottom. It could be cut with the right sized milling tool. Remove it, file the flat, and reinstall to the same torque, with a 4 or 5 foot handle on the action wrench. One thing I'd like to see some attention paid to, is designing a taper that doesn't have a natural resonant frequency. But most just turn for pretty, or hitting a max allowable weight. Such barrels tend to be quite picky about the load for best accuracy, often found by loading in slowly increasing charges, and shooting to see the movement on target as the charge is increased. The most accurate load will generally correspond to the widest swing of the string on the target because at the peak of the widest string, the barrel is moving the slowest as it peaks at the swing point at the instant the bullet leaves the muzzle. At that point, a small variation in charge or ignition has the least effect on the impact point. Change the load so its at the mid-point of that vibration, perhaps a 2% change, and it becomes much more sensitive to a .1% change in the load because that movement swing is at the highest velocity. Bug hole guns are a whole science in themselves. So are the shooters who can make them perform. At my age and eyesight today, I am long past my peak. So I cheat with ever more powerfull glass sights. I can recall a shooter on an adjacent bench in 1978, calling my attention to a fly sitting on the corner of my target, 100 meters out. I moved a few grains of sand in the bags and said "do you mean that one?" as my rifle spoke. He said I missed, so we bet a 6 pack and walked out to look at the target. The bullethole had bloodstained edges. ;-) But that was 39 years ago. And I had a Bud to wash down dinner that evening. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
