Sorry to be a little bit contrary chaps BUT........... Unless you know different and can show me where it says so in the EMER's, user or technical handbooks, there was never a reason for a soldier to un-cock his rifle from the cocked position by using the cocking piece. It would be absolutely taboo. Even if he had a misfire, he'd simply eject the round and carry on firing. Decocking was always by firing off the action.
Armourers only were taught to close the bolts during inspections etc etc by squeezing the trigger at the same time so that the cocking piece went forwards under control on the short to long cam. This is the only way in which there will be insufficient, even accidental force on the striker to set a cartridge off
This situation also arises with the Browning No2 and L9 pistols currently in use. If it's loaded and 'ready', with a live round in the chamber, then the safety is put ON and there the hammer stays. You try to 'de-cock' at your peril, knowing that a wet or cold hand and one slip will earn you a rocket up the xxxe AND a fine of 28 days pay. PLUS any damage caused. And if anyone is injured or worse, then the world will collapse around your ears.
So, unless there is a proper inbuilt means to de-cock, then don't do it. Just unload or put the safe to SAFE