As a very good "natural" I can tell you it was part of a group of shots,you might just get lucky once in a few million and hit first round but odds are very against it.
Fixed point against fixed point is good,I've been realy impressed if target had been mobile,that's nearly all luck v skill.
My best,swooping seagulls at triangulated from fixed points to have been 1800 yards,impact point out at sea so hard to properly measure,single standard 7.62mm ball,fired from L1A1,open sights,stood up.i called the shot,waited 5 seconds,cloud of feathers.witnessed by two very,very experienced UK soldiers and range control officers..
At ultra long ranges,it's luck,the target can decide to go have a wee,sit down,or anything.
There are stories of Russian troops building/converting 20mm cannons for this kind of job in Afghanistan 1. !!!