Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!cbnews!cbnews!military From: jmasly@mainz-emh2.army.mil (John Masly) Newsgroups: sci.military Subject: RE: Battleships (Condoms for Projectiles?) Message-ID: <1991Feb21.024903.9181@cbnews.att.com> Date: 21 Feb 91 02:49:03 GMT Sender: military@cbnews.att.com (William B. Thacker) Organization: AT&T Bell Laboratories Lines: 48 Approved: military@att.att.com From: John Masly steve@nuchat.sccsi.com (Steve Nuchia) writes: >I was told that during 'Nam they were worried about using up the >last of the liners and discovered that a teflon garbage bag "condom" >on the shell reduced the wear to just about zero. While coating a projectile with Teflon may reduce the barrel liner wear somewhat, it does not bring it to 'just about zero'. There are usually two points on a projectile that cause friction wear; the rotating band and the bourolette (spelling?). Teflon would reduce the friction between the bourolette and the liner, but the force of driving the rotating band into the rifling would tend to quickly remove the Teflon coating at that point, so you would get little gain in that area. Also bear in mind that friction is only one source of wear in a barrel. The other major source of wear is the action of the hot propellant gasses on the metal. As the projectile accelerates down the tube, the gasses produced by the propellant also accelerate toward the muzzle. These hot gasses erode the metal of the liner, and by far are the most significant componant of total barrel wear. >This has come up before, but does anyone have any idea how many 16"/50's >and liners still exist? Could we reline a gun if we had to? The last I recall seeing them, there were about a dozen complete 16" tubes sitting on the ground at U.S. Naval Surface Weapons Center, Dahlgren VA. I believe that Watervliet Arsenal (Army) still retains the capability to reline gun tubes up to 16". >[mod.note: I would presume they still have available 16" practice >ammunition. My reference (Friedman, _US Naval Weapons_ is on loan right >now, but as I recall this special round and powder charge increased >barrel life by an order of magnitude. - Bill ] I would guess that this practice ammo was a good deal lighter than the projectiles used for battle, thereby allowing the use of a smaller propellant charge, and therefore reducing the erosion caused by the hot propellant gasses. >From phil@zorch.SF-Bay.ORG (Phil Gustafson): >Just using HE, rather than armor-piercing ammo, eases things on the >gun a great deal. AP rounds should not cause any more (or less) wear than HE rounds, provided that the same powder charge is used in both firings.