The initial Russian invasion of Ukraine in 2014 stagnated into trench warfare after a few months, and Ukrainian forces found themselves often in entrenched positions 500m or more from Russian opposition. At that range, their PKM .30-cal machine guns were not really effective, but .50 caliber guns were. And so, they started a program of retrofitting DShK heavy machine guns with muzzle brakes (initially designed for NSV machine guns on light tripods), bipods and shoulder stocks to use as support weapons. These could be effective against targets like vehicles and strong points up to 1000m when used with good optics (or spotters with optics). Later versions also added a pistol grip and conventional trigger, instead of using the original spade grip triggers. Fitted out like this, the felt recoil is roughly equivalent to shotgun firing light birdshot loads.
DShK machine guns were standard equipment on Soviet tanks and other vehicles in the early part of the Cold War, used as antiaircraft machine guns. There is little practical AA use of this type of heavy MG against modern aircraft, and I suspect Ukraine had a significant number of them on inherited Soviet vehicles.
This footage comes from two joint US/Ukrainian training exercises, in September 2017 and February 2018. I’m sure the guns are still in use right now, and I suspect they will show up in publicized footage sooner or later. The still photos are from fighting in eastern Ukraine in 2017 (I mistakenly said 2015 in the video).
The appearance of U.S. Department of Defense (DoD) visual information does not imply or constitute DoD endorsement.