The specification for the Mark VII Ball cartridge was very precise; the bullet had to be held in place with a 3-pronged "stab crimp" and the resulting cartridge had to resist 60 pounds f force on the bullet point without the bullet moving. The reason for this was better feeding in rifles and, especially, in the Vickers MG which, being a Maxim type, cammed the round backwards in the Feed Block by sliding it past a rounded cam plate; the Gib of the Lock then picked up the round, extracted it from the Belt, chambered it, extracted it from the Barrel, inserted it into the Ejection Tube and left it to be pushed out by the next round. The Bullet of the Mark VII Ball round was a 3-piece 174-grain effort with a Jacket, Filler Plug in the nose weighing 3 grains which could be Aluminum, Fibre or Paper Wadded, with the bulk of the Core behind that. This bullet was marvellously stable at long ranges and was a very accurate bullet. It was also impact-unstable, gaining the Army back some of what they had lost when their Dum Dum Specials were outlawed by the Hague Convention.
I note that at least TWO of your rounds do NOT have stab crimps on the bullets. This means that they are not Ball ammunition but rather some sort of Specials. The precise type will be marked on the base of the Cartridge: B for Incendiary, W for AP, G for Tracer, P for very early AP, and others. There were 5 types of Tracer, 6 of Incendiary, 2 of AP and so forth. The type is always marked: WII indicates Armour-Piercing Mark II, for example. a C means that the round is loaded with Cordite, a Z that it is loaded with an extruded powder such as we use now. There also will be Factory markings and the Dates that each round was made.
I don't know how many different .303 cartridges there really are. I have over 200 here and I am not even properly started yet. Peter Labbett, the great British authority on ammunition, had more than 1800 .303s in his personal collection. When he wrote the definitive textbook on .303 development, he used his own collection and that of Mr. Bert Woodend (who had 3600 different .303s) as reference material.
Looking at your photos, I would say that you have a pretty decent start on a .303 collection!
Hope this helps.