On Monday 08 February 2016 11:23:58 andy pugh wrote: > On 8 February 2016 at 16:12, Gene Heskett <ghesk...@wdtv.com> wrote: > > One question remains: Does the thread even have to have a spiral > > component, eg does it need to actually advance into the hole as it > > turns? Common sense says it should, in order to achieve a gas tight > > seal against a shoulder at the bottom of the bore. OTOH, with a > > shell casing supplying the breach seal as modern bolt rifles do, if > > the headspace when closed is tight enough to prevent a casing head > > separation, the need for the spiraling thread is removed. > > Screwed breeches of the Welin or de Bange type are only used with > bagged charge guns. They both use a de Bange obturator for sealing > whereas a brass-case gun used the case for obturation. > This might mean they need no lead, but the pictures seem to indicate > one.
That was the impression I came away with. But explain the De Bange or Welin seal please. I am reasonable familiar with the seal method used in the front loading BP rifles asd I have a couple, and have read of the disastrous blowups that have occured in one makers version of a BP inline ignited rifle, along with the manufacturing shortcut that lead to several blowups. One such blowup was close to lethal as he was lucky to be only a few minutes from the ER door, or he would have bled out. For exactly that reason, gas cutting at the seal face of the breech plug to barrel recess shoulder, I consider either of my BP rifles to have a lifetime of 500 or fewer shots unless a reliable method of machining the gas cutting grooves back out of the sealing stopper shoulder in the barrel that the breech plug seats against. No amounty of replacing the breech plug when it can be seen to be cut will suffice to restore the seal indefinitely. Just like a leaky faucet, the seat MUST be recut smooth from time to time. The only way it seems to me, is to use a pipe thread, and no one to my knowledge is doing that. Perhaps it has a slightly different failure mechanism that is just as dangerous when the pressures exceed 20k psi? IDK. 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> ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
