After the rules changed, and DCRA/PRA competition no longer required rifles to be in service configuration, target rifles were made up on a variety of available actions. Military actions were popular because they were less expensive than commercial ones. You will see similar rifles based on P'14, M1917 actions.
This one is very nicely stocked up.
Schultz & Larsen barrels were popular.
The rifles were intended to be used with 7.62x51 ball, thus the 14" twist often seen.
No. 4 based target rifles were often considered to perform better at longer ranges - past 600y - so many competitors used 2 rifles. One like this for the shorter ranges to 500y, and a Lee Enfield based rifle for longer ranges. With issue 7.62x51 NATO ammunition, Lee Enfield rifles were thought to "compensate", and shoot groups with less vertical dispersion than other rifles. Once issue ball was no longer supplied, the No. 4 based rifles rapidly disappeared from competition.