New M2A4 being tested.
Externally, it looks the same as an M2A3 to me. I guess all the changes/updates are internal.
“The Bradley M2A4 features the latest digitized electronics for optimum situational awareness, network connectivity and communication within the Armored Brigade Combat Team. It is equipped with a wide-angle Driver’s Vision Enhancer, improved Force XXI Battle Command Bridge, and Below (FBCB2) software integration improve friendly and enemy vehicle identification, enhancing situational awareness. The addition of a High-Speed Slip Ring, greater network connectivity and Smart Displays that simultaneously display classified and unclassified information also improve situational awareness.”
Some more info on the M2A4 upgrades:
After the Iraq War, the Army began researching engineering change proposals (ECPs) for the M2 Bradley to buy back space, weight, power, and cooling capacity reduced by the addition of armor and electronics hastily added during combat.
ECP1 will work to restore mobility and allow the vehicle to handle more weight. As weight increased, the Bradley got lower on its suspension, which reduced ground clearance. This decreased mobility on rough terrain and left it more vulnerable to IEDs. The effort will install lighter tracks, shock absorbers, a new suspension support system, and heavy weight torsion bars.
ECP2 will restore automotive power with a larger engine, a new transmission, and a smart-power management system for better electrical power distribution to accept future networked tactical radio and battle command systems.
Vehicles that receive both the ECP1 and ECP2 upgrade will be designated A4. The first Bradleys upgraded with ECP1 were fielded in mid-2015, and the first to be upgraded with ECP2 were fielded in 2018.
The M2A4 is equipped with an enhanced drivetrain, more powerful engine, new digitized electronics, a new fire suppression system, and a new IED jammer. On June 14, 2018 BAE Systems Land and Armaments was awarded a contract to produce up to 164 M2A4 and M7A4 Bradley Fighting Vehicles using existing M2A3, M7A3 and M2A2 ODS-SA Bradleys.