page_title: M1 Abrams
section_title: Armor
hierarchical_section_title: M1 Abrams / Design / Countermeasures / Armor
caption_attribution_description: Deutsch: Soldaten der 1st Armored Division fahren während der Übung Ready Crucible mit ihrem M1A1 Abrams durch den Taunus nördlich von Frankfurt.English: Soldiers from the 1st Armored Division drive their M1A1 Abrams tank through the Taunus Mountains north of Frankfurt, Germany, during Exercise Ready Crucible.
context_page_description: The M1 Abrams is a third-generation American main battle tank designed by Chrysler Defense. Conceived for modern armored ground warfare and now one of the heaviest tanks in service at nearly 68 short tons, it introduced several innovative features, including a multifuel turbine engine, sophisticated Chobham composite armor, a computer fire control system, separate ammunition storage in a blow-out compartment, and NBC protection for crew safety. Initial models of the M1 were armed with a licensed-produced 105 mm Royal Ordnance L7 gun, while later variants feature a licensed Rheinmetall 120 mm L/44.
  The M1 Abrams was developed from the failure of the MBT-70 project to replace the obsolescent M60 Patton. There are three main operational Abrams versions, the M1, M1A1, and M1A2, with each new iteration seeing improvements in armament, protection, and electronics. Efforts to develop an M1A3 version were first publicly disclosed in 2009. Extensive improvements have been implemented to the latest M1A2C and D versions such as improved composite armor, better optics, digital systems and ammunition.
context_section_description: In July 1973, representatives from Chrysler and General Motors traveled to the United Kingdom, and were escorted by personnel from the Ballistic Research Laboratory and XM1 Project Manager Major General Robert J. Baer to witness the progress of British developed Chobham armor. They observed the manufacturing processes required for the production of Chobham armor, which was an arrangement of metal plates, ceramic blocks and open space; and saw a proposed design for a new British vehicle utilizing it. HEAT and sabot rounds enter the beginning layers of armor but are unable to penetrate the crew compartment. Ceramics have the ability to absorb a great deal of heat, and can blunt physical blows by cracking and deflecting the force. The remaining hot gasses and metal shrapnel spread out or settle in empty air pockets. Both contractors reevaluated their proposed armor configurations based upon the newly obtained data. This led to major changes in the General Motors XM1. The most prominent of which is the turret front changing from vertical to sloped armor. The Chrysler XM1 on the other hand retained its basic shape although a number of changes were made. The Ballistic Research Laboratory had to develop new armor combinations in order to accommodate the changes made by the contractors.
  Similar to most other main battle tanks, the M1 Abrams feature composite armor only on the frontal aspect of the hull. However, the Abrams' turret features composite armoring across both the front and the sides. In addition, the side skirts of the frontal half of the hull are also made of composite, providing superior ballistic protection against chemical energy munitions such as HEAT rounds. The composition of the Abrams' composite armor consists of sandwiched plates of non-explosive reactive armor (NERA) between conventional steel plates. The NERA plates feature elasticity, allowing them to flex and distort upon perforation, disrupting the penetrating jets of shaped charges and providing more material and space for a kinetic round to pass through, thus providing increased protection compared to conventional steel armor of similar weight.
  For the base model M1 Abrams, Steven J. Zaloga gives a frontal armor estimate of 350 mm vs armor-piercing fin-stabilized discarding-sabot (APFSDS) and 700 mm vs high-explosive anti-tank warhead (HEAT) in M1 Abrams Main Battle Tank 1982–1992 (1993). In M1 Abrams vs T-72 Ural (2009), he uses Soviet estimates of 470 mm vs APFSDS and 650 mm vs HEAT for the base model Abrams. He also gives the Soviet estimates for the M1A1, 600 mm vs APFSDS, and 700 mm vs HEAT.
  Armor protection was improved by implementing a new special armor incorporating depleted uranium and other undisclosed materials and layouts. This was introduced into the M1A1 production starting October 1988. This new armor increased effective armor particularly against kinetic energy rounds but at the expense of adding considerable weight to the tank, as depleted uranium is 1.7 times more dense than lead. The first M1A1 tanks to receive this upgrade were tanks stationed in Germany. US-based tank battalions participating in Operation Desert Storm received an emergency program to upgrade their tanks with depleted uranium armor immediately before the onset of the campaign. M1A2 tanks uniformly incorporate depleted uranium armor, and all M1A1 tanks in active service have been upgraded to this standard as well. This variant was designated as the M1A1HA (HA for Heavy Armor). The M1A1 AIM, M1A2 SEP and all subsequent Abrams models feature depleted uranium in both the hull and turret armor. Each Abrams variant after the M1A1 have been equipped with depleted uranium armor of different generations. The M1A1HA uses 1st generation armor, while the M1A2 and M1A1HC use 2nd generation depleted uranium. The M1A2 SEP variants have been equipped with third generation depleted uranium armor combined with a graphite coating. The M1A2C also features increased physical line-of-sight turret armor.
  For the M1A1HA, Zaloga gives a frontal armor estimate of 600 mm vs APFSDS and 1300 
caption: Tankers drive an M1A1 Abrams through the Taunus Mountains north of Frankfurt during Exercise Ready Crucible in February 2005.
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