There is a patent for a electronically enabled bullet dodging capability. If a sniper is firing from 2500 meters then there is 4 seconds to move out of the way if the bullet can be detected as it emerges from the muzzle. (H/T to Firearm blog
The knee reflex takes about 20 milliseconds to fire. Bull riders can have head accelerations of 26-46 Gs (258-450 m/s**2). So 40 m/s**2 head acceleration should be safe, although it could be necessary to move someone faster and get whiplash instead of a bullet hole. Moving about 15 centimeters would often be enough to get out of harms way.
Considering a rather short, 200 meter shot, a time of flight of about 200 milliseconds is available from the time of firing until the impact. The typical contraction time of human muscles is between about 40 milliseconds and 80 milliseconds, thus providing sufficient headroom for the electronics to compute the optimal avoidance strategy and initiate evasive muscle stimulation (which will only be limited by the ability of the body to follow the electrical stimulus).
Guided Bullets - Could React to Dodging Target
Darpa, the Defense Department's far-out research arm, announced a pair of contracts to start designing a super, .50-caliber sniper rifle that fires guided bullets. Lockheed Martin received $12.3 million for the "Exacto," or Extreme Accuracy Tasked Ordnance, project, while Teledyne Scientific & Imaging got another $9.5 million.
Darpa won't say, publicly, how far, how long and how accurate they want the new bullets to be — all that information is classified. But they will say that Exacto should contain a next-gen scope, a guidance system that provides information to direct the projectile, an "actively controlled .50-caliber projectile that uses this information for real-time directional flight control," and a rifle. "Technologies of interest may include: fin-stabilized projectiles, spin-stabilized projectiles, internal and/or external aero-actuation control methods, projectile guidance technologies, tamper proofing, small stable power supplies, and advanced sighting, optical resolution and clarity technologies."
So if both bullet dodging and real-time guided bullets were successful, then there would be a lot of moves and counter-moves going in split second. [a bullet-time battle]
It would also be Matrix Bullet Dodging versus Angelina Jolie in Wanted curving bullets.
Counter Sniper Systems - Detecting and Suppressing Snipers
DARPA is working on counter sniper systems This would be thrown into the mix of dodging versus guided with detection and suppressing fire at the point of a shot being taken or even before.
C-sniper (counter-sniper) program, which aims to detect and neutralize enemy snipers before they can engage US Forces. Given that snipers don't advertise their presence before the bullet crack, the C-sniper system is expected to operate in always-on mode from a moving vehicle. Presumably, the signatures to be exploited can be inferred from DARPA's own offense programs – e.g. radiation from laser scopes, or reflections off optical scopes.
C-sniper is actually a follow on to a larger programme called Crosshairs. Managed by TTO, Crosshairs is aimed at producing systems to detect enemy bullets, RPGs, (ATGMs) and mortars fired at US military vehicles and to prevent them from striking the vehicle. Incredibly, threat identification and localization will be accomplished in sufficient time to enable both automatic and man-in-the-loop responses.
Wired talks about c-sniper program
Cops and soldiers now have the ability to pinpoint incoming sniper fire. The military's way-out research arm wants to take that a step further, by finding and "neutralizing" shooters before they ever pull their triggers.
For years, military engineers have been working to build a similar system -- using flashes of laser light to "illuminate potential hiding places... and detect retro-reflections from the sniper’s scope.
An infrared camera/illuminator uses backscattered infrared (808 nm) illumination to light up an area of interest at distances up to 1 km. Optical augmentation (glint) from an individual's rifle scope/binoculars or even a person's retinas provides a means of detecting that individual.
Jet Propelled or Mechanically Assisted Bullet Dodging
If you were not relying upon muscle but something in the exoskeleton to propel the body or body part out of the way then faster short movements could be possible. A jet of gas could be used to move the head or body to initiate the dodge along with muscle activation.
A method of protecting a target from a projectile propelled from a firearm comprises detecting an approaching projectile, continuously monitoring the projectile and transmitting an actual position of the projectile to a controller, computing an estimated projectile trajectory based upon the actual position of the projectile, determining an actual position of a target with a plurality of position sensors and a plurality of attitude sensors, determining whether the estimated projectile trajectory coincides with the actual position of the target, and triggering a plurality of muscle stimulators operably coupled to the controller and to the target when the estimated projectile trajectory coincides with the actual position of the target, wherein the muscle stimulators stimulate the target to move in a predefined manner, and wherein the target moves by an amount sufficient to avoid any contact with the approaching projectile. The projectile may be detected in the detecting step by emitting an electromagnetic wave from a projectile detector and receiving the electromagnetic wave after the electromagnetic wave has been reflected back toward the projectile detector by the projectile.
Sniper Rifle Ranges and Typical Shot Distances
Effective range for the standard-caliber sniper rifles against the single human-sized target may be estimated as 700-800 meters for first-shot kills. To extend effective range beyond 1000 meters, often used sniper rifles, designed to fire more powerful ammunition, such as .300 Winchester magnum (7.62x67mm) or .338 Lapua magnum (8.6x70mm). The range for sniper fire may vary from 100 meters or even less in police/counter-terror scenarios, or up to 1 kilometer or more - in military or special operations scenarios.
How Stuff Works describes "How Military Snipers Work"
A Canadian sniper in Afghanistan made the longest recorded sniper kill in history with this weapon. On a March afternoon in 2002, Corporal Rob Furlong of the Princess Patricia's Canadian Light Infantry (PPCLI) killed an enemy combatant from 2,430 meters (12.0772 furlongs/2,657 yd/1.509 miles) with American 750 grain Hornady A-MAX very-low-drag bullets.
Current Sniper Shot Detection Systems
Shotspotter is the audio-monitoring tool used by law-enforcement agencies to pinpoint gunfire. They use a triangulation system to coordinate with other nearby Shotspotter devices to determine precisely where gunshots are fired. They have a range of about 2 miles and are guaranteed accurate to within about 75 feet, though typically they are closer to the exact location. This is nowhere near the accuracy and speed needed for the bionic bullet dodging system. The current systems are for determining an area to cordon off so that the sniper can be hunted in city block or four city blocks or in a section of jungle. Meanwhile the target of the sniper is assuming room temperature.
Detection of the shot and the precise trajectory of the shot will have to get a lot better for bionic dodging to know the direction to dodge and the point to move away from.
Phil Helmuth: I can dodge bullets baby
Wanted - bullet curving assassins