The typical barrel of a high-power rifle has exterior grooves, called flutes, to reduce weight and create more surface area to enable the barrel to cool faster. The barrel heats up as a result of the hot expanding gases in the barrel and the friction from bullets that are propelled by these hot gases along a helical path inside the barrel.
But with modern high-calibre rifles boasting ranges of up to two miles, even very small deflections in the barrel due to effects such as heating can cause a marksman to miss by a wide margin.
With the ORNL Reticle Compensating Rifle Barrel Reference Sensor technology, glass optical fibres are placed into the flutes. A laser diode then sends a beam into the optical fibres parallel to the bore axis of the barrel.
’The optical fibres are designed to split the laser beam twice, sending one beam along the top of the rifle barrel and another light beam along the side of the barrel,’ Rajic said. ’Thus, we can measure both the vertical and horizontal barrel deflection.’
Through a combination of algorithms, optics and additional sensor inputs, the system can take into account distance and other factors affecting the trajectory of a bullet. Ultimately, the marksman is left with crosshairs that automatically adjust for conditions in real time.
The resolution of the sensor is claimed to be 250 times better than that of traditional reticles. While they can normally be manually adjusted by one fourth of a minute of angle, the ORNL sensor can sense angular displacement and shift the reticle by one thousandth of a minute of angle.