Path: spln!rex!extra.newsguy.com!lotsanews.com!nf3.bellglobal.com!sunqbc.risq.qc.ca!nntp.flash.net!news-out.visi.com!hermes.visi.com!gemini.tycho.net.POSTED!not-for-mail Approved: sci-military-moderated@retro.com Return-Path: news@cantuc.it.canterbury.ac.nz Delivery-Date: Mon Oct 15 19:50:52 2001 Delivery-Date: Mon, 15 Oct 2001 19:50:52 -0700 for <sci-military-moderated@retro.com>; Mon, 15 Oct 2001 19:50:51 -0700 (PDT) id 15tK4D-0001Rz-00 for sci-military-moderated@moderators.isc.org; Tue, 16 Oct 2001 04:34:53 +0200 16 Oct 2001 15:34:51 +1200 (NEW ZEALAND STANDARD TIME) Date: Tue, 16 Oct 2001 15:34:19 +1300 From: Kerryn Offord <kao16@student.canterbury.ac.nz> Subject: Re: Smooth bore vs rifled gun barrels on Abrams To: sci-military-moderated@moderators.isc.org Message-ID: <3BCB9CAB.DF75468C@student.canterbury.ac.nz> Organization: University of Canterbury X-Complaints-to: abuse@canterbury.ac.nz MIME-version: 1.0 X-Mailer: Mozilla 4.76 [en]C-CCK-MCD (WinNT; U) Content-type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-NNTP-posting-date: Tue, 16 Oct 2001 02:34:49 +0000 (UTC) X-Accept-Language: en,ja,zh,zh-CN,zh-TW,ko Newsgroups: sci.military.moderated X-NNTP-posting-host: pug2434.psyc.canterbury.ac.nz References: <3BC9D3BC.48122855@c0.comm> <3bcb54e4.32872447@news.iafrica.com> Content-Length: 1741 Lines: 42 NNTP-Posting-Host: 50d5acf8.newsreader.tycho.net X-Trace: 1003212974 gemini.tycho.net 322 205.179.181.194 X-Complaints-To: abuse@tycho.net Xref: spln sci.military.moderated:39650 Eugene Griessel wrote: > > "Zonie! remove the excitation mark and 1 M for real email address" > <Zonie!@c0.comm> wrote: > > >The M1A1 Abrams converted to a smooth bore from a smaller rifled bore. > > > >What advantages does a smooth bore give you? > > The main ammunition for anti-tank work is an armour piercing fin > stabilised discarding sabot round. The so-called "long-rod" > penetrator. While spinning a shell helps to stabilise it it does > subject the round to precession. This means the point tends to wander > in a small circle. This is less than desirable when you want to punch > a hole through armour by brute force. You want a "square" hit so that > all the force is concentrated on one spot. Also, with a need for higher velocities to penetrate armour the fin stabilized long-rod can be accelerated to higher velocities from a smooth bore than a rifled gun. The gas seal on a rifled round has to be metal-on-metal contact between the round and the barrel this has a high friction co-efficient - limiting acceleration of the rifled round - possibly why a longer barrel allows higher velocity (but it has an upper limit where gas pressure is no longer able to accelerate against the friction). On a fin-stabilized round the gas seal can be plastic etc (any suitable low friction material). There are no edges inside the barrel to inhibit acceleration (rifling). So more energy is expended accelerating the round (than equivalent rifled round) allowing higher velocities from a shorter barrel. Advantages (IMO): 1) Cheaper barrels (no rifling) 2) Longer lasting barrels (no rifling to wear) 3) Shorter barrels (see 1 above) 4) Higher projectile velocities - better armour penetration (from shorter barrels). 5) etc