what do you think why
By your scenario, Jeremy would have to be so devious and clever to 'plant' the bullets on the kitchen worktop, with exactly 30 remaining bullets, set against the fact that there are 50 bullets in a newly opened box, and 25 rounds fired during the incident, with five of the corresponding bullet cases bearing double magazine marks indicating that at least 5 of the 25 shots fired came from a different source, and yet the same Jeremy supposedly hid the silencer away in a cupboard in the den containing all the damned blood and paint evidence that was visible to the naked eye. The two scenarios do not sit well together, it couldn't have happened like your suggesting, unless of course that Jeremy had been Sheila's accomplice...
But he wasn't, because 'Ralph Neville' was...