I just sectioned the case of this beautifully designed, 105MM APFSDS-T “EXCALIBUR” tank round. This is one of my favorite 105MM APFSDS-T projectile designs. It has by far the largest forward sabot petal holes that I have ever seen in any DS tank round with the exception of an experimental 105 that I have which is closely related to the Excalibur. I was told that these holes both aid in sabot seperation and reduce parasitic weight.
This is what Jane’s Ammunition says about the EXCALIBUR.
The 105 mm Excalibur Armour-Piercing Fin-Stabilised Discarding-Sabot Tracer (APFSDS-T) cartridge is the result of a joint development by Primex Technologies (now General Dynamics Ordnance and Tactical Systems (GD-OTS)) of the US, Giat Industries (now Nexter) of France and Royal Ordnance (now BAE Systems Land and Armaments) of the UK. It was based on experience gained during the production of the 105 mm FP105/C76 APFSDS-T (see separate entry). The design was based on the use of standard US Army components, where applicable. GD-OTS claimed that the Excalibur has a similar penetration performance to the first generation of 120 mm APFSDS rounds. This round had been marketed by GD-OTS, Nexter and BAE Systems Land & Armaments under the name of Excalibur, although limited effort appears to have been expended in the marketing by any of the companies in the last five years and the programme may well have subsequently been dropped. It was also known as the XC127 in the US but never qualified or produced there.
The 105 mm Excalibur APFSDS-T is a fixed round, with the projectile assembly securely crimped to a steel M148A1B1 cartridge case, although an alternative brass case is also available for the Excalibur. The projectile assembly consists of a subprojectile and a sabot. The subprojectile consists of a monobloc long rod tungsten alloy (X27X) core with a high length-to-diameter ratio acting as the penetrator rod. The front part of the penetrator rod has a titanium carbonitride cap and an aluminium windshield, with a steel tip to withstand aerodynamic heating effects. An aluminium six-vane fin assembly is fitted to the rear of the penetrator rod. The fin assembly also contains a tracer element, held in place by a threaded plug and disc assembly.The double-ramp style sabot is constructed from high-strength aluminium alloy (7150-T61511P) and consists of three 120° segments assembled around the subprojectile. It is interfaced with the penetrator body by a series of mating buttress grooves spaced at six grooves in 25.4 mm. A stainless-steel bourrelet with three shear points, is screwed to the forward face of the sabot to act as a bore rider. A two-part nylon obturator and polypropylene seal unit is assembled around the rear bearing surface of the sabot, and a silicon rubber seal is applied over the rear area of the projectile (ramp/rod interface).The M148A1B1-pattern cartridge case has a modified M120 electrical primer fitted to the base. The primer includes a flash tube extending almost to the tail of the projectile assembly. [/i][/b][/quote]
Hard to tell from this photograph, but the tracer cavity in this specimen is filled with a green polymer substance. I was told that during testing they did not fit the projectiles with its tracer assembly. To replace the tracers weight, the Engineer / Testers would inject the exact weight of the tracer with this green polymer substance. I was told this also keep gases out of the tracer cavity during testing that could affect trajectory and stabilization. These guys are so smart!