In trials against armour he demonstrated that the shot shaped like a punch was the most effective for the purpose. The principle still holds good, but of course modern projectiles are fitted with ballistic caps to reduce air resistance.

The calibre of Whitworth projectiles was measured across two opposite flats. The precision of their manufacture was probably the chief reason why his guns did not become popular. Projectiles were very accurately planned to shape, a more difficult process than turning, and fitted the bores extremely closely. Obviously neither bores nor projectiles were suited to mass production. Furthermore reports from America indicated bores had to be kept scrupulously clean at all times, not always possible on the battlefield, otherwise projectiles were inclined to jam.

Whitworth's system applied to small arms worked very well as already shown. Some of his rifles found their way to New Zealand and examples may be seen in the Army Memorial Museum, Waiouru. Outwardly they closely resemble the Pattern 1853 Enfield.