Cases were hand-charged by lines of women in the ordnance factories using previously prepared correct size / weight bundles of the Cordite rods. This couldn't be done with the shoulder/neck formed, so that step followed case-charging.
Since heat was obviously out of the question after Cordite charging, the shoulders / necks were cold-formed and final annealing of the area was impossible. This led to reduced ammunition storage time for some batches as necks would split longitudinally under the stress imparted by the bullet if left for enough years. I had an old, now late, friend who was upset when he bought a large sealed can of Cordite 303 to find that although in beautiful shiny well-preserved condition, getting on for half had split necks after 20 or 30 years storage.
UK Royal Ordnance Factory Radway Green (still going, now as part of BAe) loaded Cordite 303 until the changeover to 7.62 in the late 1950s, when propellants changed to conventional ball or stick types. 303 manufactured abroad (a lot in the USA during WW2) used what the British War Office and army ordnance people called 'nitrocellulose' powders and had a lower-case letter 'z' added to the cartridge designation. So canisters and cardboard packages of the standard infantry Cordite 303 model were Mk7 and the US imports Mk7z. (Bruce Hodgdon got one of his early surplus powder successes from this source. Winchester Western had loaded a vast shipment of Mk7z for the US Government late in the war as part of a Lend-Lease deal with the UK and was left holding the baby in August 1945 when Imperial japan surrendered and HMG cancelled the order. This used an early Olin Corp / WW ball powder designated Western Ball Lot C and when the US Government contracted someone to demill the many million cartridges, yielded up 80 US tons of the powder which Hodgdon bought and sold on as Hodgdon BL-C, predecessor of today's H. BL-C(2) )
The last surplus Cordite 303 ammo I saw was early this century when a large consignment of Mk7 and Mk7z from South Africa appeared on the surplus markets (manufactured in SA with its own military designation). Cordite ammo produced a distinctive grey-white smoke and unmistakable smell on firing. As
@Chubbs says it was pretty erosive thanks to ~30% nitroglycerin content. (Early pre-1910 marks of Cordite 303 had ~60% and was really erosive!) This was deemed OK for infantry rifle and LMG rifle use, but specialised machinegun ammo was not only heavier ball, but higher pressure and used 'z' type propellants as Cordite wore barrels out too quickly in sustained fire (which the water-cooled Armstrong Vickers MG was superb in and often so used). Many UK historic arms shooters (and target Service Rifle discipline) shooters preferred the Cordite version - and an Enfield Number 4 rifle could be rebarreled quickly and cheaply with millions of barrels made and thousands surviving the 1957 changeover to 7.62mm and the FAL rifle. Some Bisley SR competitors changed barrels at the beginning of the season, and again mid-way through as a matter of course. Fultons on the range premises did it in a half-day if pre-booked. The No.4 and 303 Mk7 ordnance ammo survived in UK first-line competition until the changeover to 'Target Rifle' in 1968, and a primary reason for changing from SR to TR was that the UK MoD advised our NRA in the early 60s that Mk7 production was being stopped with the military changeover to 7.62mm and that supplies of 303 couldn't be guaranteed after 1967.
