The motivations for reloading ammunition are broad. For some shooters, it is about cost savings, although that is increasingly being challenged as component costs have risen over the last few years. For precision shooters, being able to fine tune ammunition to each individual rifle can yield greater accuracy in competitions. Some are motivated by the availability of ammunition in their locale. However, for many, reloading is an enjoyable pastime which forms part of their rifle stewardship.
A major transition is underway in the supply of ammunition with the phase-out of lead bullets. New non-lead projectiles are flowing into the marketplace utilising brass, copper, zinc and an assortment of composite constructs. Many of these new bullets need evaluating, not just in terms of accuracy but in their performance and efficacy in terms of deer welfare.
Traditionally, many reloaders take their lead from load data made available from the projectile and powder manufacturer’s loading manuals and websites. A voice of warning, manufacturers test their published loads in controlled settings with pressure monitored barrels and precision measuring equipment. Loading ammunition with data from some fellow on an internet forum is not recommended for obvious reasons. Handling and loading powders that create barrels pressures approaching 60,000 psi require care and total attention. This lag in the availability of load data by the suppliers is a genuine concern.
One effective way of modelling the characteristics of new ammunition loads is the use of an internal ballistic simulator program. Historically, the go-to product has been the excellent, but ageing QuickLoad (£139).
Internal ballistics (IB) programs have the potential to remove a lot of guess work and can be an invaluable tool for reloaders. A private initiative to build a new reloading and data crowd sourcing platform was initiated. Initially out of pure interest, the author of Gordons Reloading Channel decided to deal with the topic of interior ballistic simulation calculation and to develop his own software after studying the relevant literature. Experience in thermodynamics, physics and software development from his professional career were helpful. The author built a development team from reloading/programming enthusiasts, and created an IB program called Gordon’s Reloading Tool, GRT for short. GRT is supplied for free and is supported through voluntary Patreon contributions. It is available for both Windows and Linux operating systems. As a Mac user, GRT can be seamlessly run with emulators such as Parallels, VMWare Fusion and Crossover (no requirement to install a copy of Windows) or by directly booting up Windows on a Mac Bootcamp partition.
Internal ballistics refer to the processes inside a barrel during the firing of a weapon, from the time the propellant is ignited until the subsequent gas pressure sends the projectile out the muzzle. The study of internal ballistics involves the properties of the weapon and components, the pressures created by the burning propellant, the influence of these on bullet acceleration and the resultant muzzle velocity of the projectile. Pressure and velocity can be projected by an IB program and has the potential to remove a lot of guess work and be an invaluable supplementary tool for reloaders. These software platforms were previously only used by and available to the major players in propellant manufacturing and research.
The GRT platform is divided into input and output windows. A user chooses their calibre, bullet measurements and propellant (powder) from the extensive and up to date GRT databases or custom user created files. The physical properties such as barrel length, case volume, case length, cartridge length and charge load are entered into the program. The software algorithms then mathematically compute the behaviour of the components during the firing process and produces the resultant internal pressure curve and muzzle velocity. From these results a loader can get insight into the outcomes of a proposed load, most importantly checking whether the resultant pressures are safe.
A user can customise the GRT interface and choose between a basic and expert mode. In the expert mode each input window provides and/or displays all detailed value entries, such as all powder-specific coefficients and constants. In addition, a cartridge drawing of the original (CIP) calibre specification including all dimensions is visible in a separate window.
At first look, GRT can be overwhelming, which explains why the developers offer a basic mode version. However, after reviewing the comprehensive manual, accessed from the main menu, a reloader will soon be able to model a proposed load.
The interface is aesthetical pleasing and logical. It rather ages QuickLoad, which appears unchanged since the days of Windows NT. Operating GRT in dark mode is particularly gentle on the eyes.
In both modes of operation, there is toolbar access to some notable tools, they include the following:
• conversion unit tools
• a table of propellants
• calculator for effective cross section of the calibre/barrel
• black powder calculator
• shot group analysis
• optimal barrel time (OBT)
• parametric powder search and general tolerance synthesis
• cartridge designer
The parametric powder search tool provides an ability to compare powders with equivalent outcomes and is a particularly useful feature. In the event a reloader has worked up a preferred load but can no longer access a manufacturer’s powder they can use the synthesis algorithms to model similar pressure and velocity outcomes with very high levels of precision.
As well as sourcing data from existing literature, laboratories and manufacturers, users with a chronograph can share their load and velocity data directly to the GRT Lab through a plugin app. This data is then used to further evaluate and tune the accuracy of the powder modelling algorithms.
Using a mobile phone to photograph range targets enables a user to download their shot photographs to GRT, the program will then automatically dimension and analyse the shot groups. Notes and scores can be added in relation to the groups. By utilising a Labradar, ProChrono, Caldwell, PressureTrace II or MagnetoSpeed chronograph, projectile speed files can be directly imported from the device into GRT for specific shot profiling and storage. The doppler based Labradar chronograph enables tracking analysis which can be displayed showing the projectile speeds down the range in the main output section.
GRT is equipped with an elegant array of reporting options. The default choice is between compact and detailed formats and like the interface they are well designed. However, for those accustomed to using a simple syntax similar but simpler than HTML, it is possible to create custom reports.
Although few people will ever use the cartridge designer tool or have access to rifle pressure gauges, the capabilities are built-in for powder and component manufacturers and research labs to deploy.
The team at GRT has successful built an active and engaged community from all around the World with 35,000 users, 28,000 being active on the site. The community can be fully accessed through the Discord app. GRT is constantly being enhanced with new data and it is noteworthy how quickly new calibres, powders and projectiles are added to the databases. The team provide advice and are clearly open to suggestions on ways to improve and further develop the program. This is impressive software on so many fronts and the fact that it’s freely available, makes it even better. Perhaps if you do decide to use GRT, then you may wish to make a small contribution to this splendid team of developers via Patreon. https://www.patreon.com/gordonsreloading
If considering reloading, you would be well advised to enrol on a reputable course. Software can enhance an understanding of producing ammunition but there is no substitute for well supervised hands-on experience. Even for the experienced reloader, the best advice is always work up your loads and watch for pressure signs. IB software such as GRT can provide a safe and effective starting point for load development.
www.grtools.de
