Many of us have watched military units performing rifle drills in parades. The USMC's Silent Drill platoon is one of the more well known units here in the US. How many of you know that the rifles they use are inert? That is the subject of today's post: the Drill Rifle.
A drill rifle is based on a normal rifle, but it has one key difference: it cannot actually be fired. So why make a firearm that cannot be fired? It can be used to train cadets on the use of a rifle, before they go out and fire the real thing. It can also be used safely for drill demonstrations. It cannot be used by a disgruntled cadet to take shots at a crowd or a chief guest (yes, this has happened in the past in some countries). In the UK, the Lee Enfield L59A1 Drill Rifle was specifically developed because there was some concern about the Army Cadet Corps and Combined Cadet Corps having their equipment stolen by the IRA.
Modifications from a standard rifle include clipping the firing pin short so that it can't impact a round in the chamber, welding the barrel shut, welding the striker hole in the bolt shut, welding the barrel to the receiver so that it can't be removed and fitted with another barrel, removing locking lugs, cutting part of the barrel internally, removing sights etc.
The end result: a rifle that looks very close to the real thing, but is incapable of firing and needs a large number of modifications before it will ever come close to firing anything. The USMC Silent Drill platoon uses inert versions of the M1 Garand rifle and US Navy uses inert versions of the M1903A3 Springfield rifle for their drill purposes.