Untitled By Julian Nettlefold, Reports emanating from Ukraine demonstrate the effectiveness of current 30mm canon systems against Russian APCs and the BMP-4 in particular. This puts a big question mark over the threat analysis conducted in the 1990s which saw a need for 40mm and the CT-40 canon in particular, to defeat the BMP-4. Has the decision by the US to go for 50mm in 2020 also been found wanting? The Argument for 40mm So how does CTA technology allow the CT40 cannon to perform above its competition? Due to the nature of telescoped ammunition, CTA ammunition has 30 percent more performance for the same volume of ammunition. This can be seen in a comparison of the size of the rounds: forty-millimeter CT ammunition is only the size of conventional thirty millimeter ammunition while delivering performance on par with conventional forty-millimeter rounds. Talking in numbers, the forty-millimeter CT Armor Piercing round can pierce 150 millimetres of armor at 1.5 kilometers. This is sufficient performance to defeat any current BMP-series IFV and their upgrades. This is superior to the hundredmillimeter-plus RHA at one kilometer offered by the 30x173-millimeter rounds used by the latest versions of the U.S. Army’s thirty-millimeter Stryker. The airburst capability of the forty-millimeter CT rounds is also superior, more than doubling the affected area versus thirtymillimeter rounds. All of this comes in a package that is around the same size and bulk as the thirty-millimeter cannons. The CT40 cannon can also hold more rounds in the ready position, around a hundred ready rounds compared to the twenty-four to twenty-five ready rounds that are possible with the Swedish fortymillimeter L/70 cannon on the CV9040, as reported by Jane’s. This is due to a novel rotating breech that is deployed on the CT40 cannon, as well as a linkless ammunition-feeding mechanism, made possible by the geometry of the CTA rounds. Alternative Systems The lack of take-up of 40mm as the calibre of choice was underlined in December 2021 when the US Army rejected a 40mm solution and went for the Northrop Grumman XM813 Bushmaster Chain Guns®. Northrop Grumman XM813 Bushmaster 30/40 Northrop Grumman offered the UK an upgrade to the Bushmaster 30, the Super Forty which used the same systems as the 30mm upgraded to support a 40mm round. The UK MoD never considered this and decided to go sole source to CT-40 even though the Bushmaster Super Forty offered commonality to the 30mm, thus reducing costs and the logistics footprint. The 30mm/40mm XM813 Bushmaster® Chain Gun® automatic cannon is a next generation weapon available, battleproven and in use today. It continues the Bushmaster® tradition of excellence with its design simplicity, external power, positive round control, ease of maintenance, and constant velocity ammunition feed. The XM813 is also capable of firing the new programmable air burst munitions. What’s more, it incorporates all of the battle-proven features of the 25mm M242 Bushmaster® Cannon®, with significant system commonality for low-risk, proven performance. Northrop Grumman Corporation (NYSE: NOC) was awarded a contract in 2020 from the U.S. Army for XM813 Bushmaster Chain Guns® as part of the Stryker Medium Caliber Weapon System 30mm Lethality Upgrade program. The base contract and first delivery order called for 95 chain guns with initial deliveries beginning in early 2022. The XM913 is an experimental American chain gun produced at Picatinny Arsenal. The cannon is a larger and more modern version of the 25 mm Bushmaster cannon. Although its shells, 50 x 228mm, are twice the diameter of the 25mm M242 Bushmaster, the 50mm cannons is not much longer than the smaller weapon. The overall lengths of the 25mm cannon and 50mm cannon are 105.2 inches (267cm) and 117.7 inches (299cm), respectively; while the portion of the gun that intrudes into the turret are 30.0 inches (76cm) and 40.1 inches (102cm), respectively. The XM813 is a 30x173mm caliber cannon and a derivative of the company’s Mk44 Bushmaster Chain Gun® integrated on air, land and naval platforms across the globe. The XM813 was initially fielded to meet the urgent operational need to ‘upgun’ the 2nd Cavalry Regiment’s Stryker fleet based in Germany to provide crews with increased capability to defend against emerging threats. The current contract will support enhancements to the XM813 and the integration of the chain guns into an additional U.S. Army Brigade Combat Team. The XM813’s versatility allows for the incorporation of future advancements, including the ability to fire Northrop Grumman’s advanced ammunition types which will ultimately include proximity fuzed and guided munitions. Currently, the XM813 is capable of firing Northrop Grumman’s MK310 Programmable Air Bursting Munition (PABM) with air-burst, point-detonate and point-detonate with delay fuze settings to defeat a variety of targets. The chain gun production will occur at Northrop Grumman’s Mesa, Arizona facility.
