Probably been submitted already and maybe no one but me cares but here it is anyways

  1. Choose a weapon with a magazine actuated bolt/slide catch (M4, SCAR, any pistol)
  2. shoot 1 round
  3. proceed to reload, during the reload swap to another weapon once the magazine is removed.
  4. swap back to original weapon and fire the chambered round.
  5. the weapon will lock it's bolt/slide to the rear.

Since we removed the magazine in step 3 and then fired the weapon the bolt/slide should not be locked in place. Firearms like the M4 rely on the magazine to push the bolt catch up to catch the bolt and similarly for pistols the magazine typically pushes the slide stop up to catch the slide.

The reload animations should have the character model racking the slide or using the charging handle once a new magazine has been inserted.