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Itching to write a new GPC article

Posted 01-31-2015 at 04:41 PM by ttk

It's been more than two years since I wrote something about the General Purpose Cartridge for military rifles

I wanted to hold off so I could improve my ballistic analysis software, collect more empirical evidence, and learn something about the GPC candidates and legacy cartridge upgrades under development by various military institutions, but these developments have been slow in the coming.

When I've had time to spare for my Physics::Ballistics software modules, I've spent it improving the packaging, return semantics, unit tests, and documentation, so I can submit them to CPAN. Thus improvements of the algorithms themselves have been sporadic and scant. In particular, algorithmic treatment of lethality and cartridge weight have proven quite the rabbit-holes, and it will be a while before I've plumbed their depths. In my defense, they seem better in ways than the technologies in use by other participants.

In the meantime, I've been reading what Anthony Williams, Nathaniel Fitch, and others, have had to say, and they've brought up several points, some good, others not so much, which I'd like to inspect and expound upon. Also, political influences have overshadowed some technical aspects of potential solutions, and those should be addressed.

So I'm going to write a third article soon, putting aside my misgivings about shortages in technology (but not too far -- I will note them in the article; full disclosure is, IMO, far more important than proving myself "right").
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  1. Old Comment
    May I ask, how you got into this research? It's interesting.
    Posted 02-05-2015 at 05:08 PM by vmccord vmccord is offline
  2. Old Comment
    Originally Posted by vmccord View Comment
    May I ask, how you got into this research? It's interesting.
    Somewhat indirectly.

    About fifteen years ago, I became interested in the material science of composite armor. One of my mentors in the subject, Paul Lakowski, invited me to the Tank-Net military forums, where I became acquainted with Anthony Williams, who is championing the GPC concept to the UK Defense Ministry and is a Tank-Net regular.

    In order to understand armor, and to design armor to defeat a threat, it is necessary to become familiar with the threat it needs to defeat, which meant that my interest necessarily spilled over into the study of things which seek to penetrate armor -- long-rod penetrators, shaped charges, shell case fragments, and bullets.

    To this end, I had already built out a few formulae for predicting the ballistic behavior of small-arms projectiles. Tank-Net is a gift culture, where everyone helps everyone else with their interests, and gets helped in turn with their own -- kind of like LQ, but with militaria rather than Linux. In this spirit, I tried to apply my formulae to the GPC discussions, to foment better understanding.

    I quickly discovered that my formulae (which mostly dealt with penetration) were woefully insufficient to the subject. The GPC issue touches on matters of internal and external ballistics, and on more terminal ballistics than just penetration. Just as important are munition total weight, barrier defeat, and wounding, which I'd never considered before.

    An engineer's got to engineer, and I've been digging in and figuring things out, collecting other people's formulae and a few of my own into Ballistics Perl modules which I can use in my perl calculator. These are still very much under development, and likely will be for some time.

    The formula for estimating the weight of empty brass cartridges is somewhat wrong, for instance. It is fairly accurate when a cartridge was designed for a given volume and peak pressure, but many cartridges are actually derived from larger/heavier cartridges (the 6mm PPC from the .220 Russian, for instance, and the .243 WSSM from the .300 WSM), which makes them heavier than they "need" to be, and heavier than Physics::Ballistics::Internal::empty_brass() predicts. Thus some of the weights in my second GPC article are wrong, which is something the third GPC article will address.

    I've started writing that article, but it's slow going. I want to touch on a wider variety of topics in it than I did in the first two articles, and it's in competition with other personal projects for my time and attention.
    Posted 02-10-2015 at 10:49 AM by ttk ttk is offline
    Updated 02-10-2015 at 11:03 AM by ttk
  3. Old Comment
    That is really different. Thanks for explaining your interest.
    Posted 02-11-2015 at 10:14 AM by vmccord vmccord is offline


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