Just because they were using .45 prior to the Hague doesn't mean they still could not adopt it; note it has nothing to do with the actual caliber, but rather the adoption of FMJ rather than soft lead-nosed or expanding hollow-point style bullets. It doesn't refer to the pointyness of the bullet either; round and flat nose jacketed bullets were not excluded.
Furthermore, the British .303 was explicitly designed to increase tumble with penetration by back weighting the bullet; the center of gravity was shifted to the rear the nose, behind the pointed jacked was packed with a lighter material.
I'd dig up the website I found this info on, but frankly I am not in the mood.
Have a nasty head cold.
Sorry about the head cold dean
I hate those things and hope you feel better soon.
Regarding the specific history of the .303 I am not particularly familiar. If it was deliberately designed to fragment I would be interested to document that information. Most jacketed, soft-metal core bullets will fragment if they strike flesh at high enough velocity. Indeed, at hyper-sonic velocities almost any substance will fragment to the point of vaporizing (I'm speaking of orbital velocitys and not small arms here). I do know that the British continued to use lead bullets in their handguns until the Germans protested in WW1 even though these are not, by the Hague definition, specifically designed to expand or fragment.
The concern that prompted the Hague prohibition was the invention, in the very late 19th century of hollow point bullets. International agreement had already prohibited exploding bullets for anti-personnel use and, with the Hague, was prohibiting rapidly expanding bullets for the same reason; not that lethality was the concern, but rather the maiming potential to those who survived being struck; arms and legs would be lost to otherwise debilitating, but non-crippling, wounds.
That the pointed Spitzer ballistic shape would tumble when it hit something was secondary to the increase in effective range that it produced. Indeed the Nazi V2 missle was based, in shape, upon the 7.92mm Mauser bullet then in use and, of course, this was not because it tumbled; likewise artillery shells share the same shape.
Short stubby pistol bullets, even if they do tumble, act more like a round ball; rarely having more than half again the diameter in length. For this reason, it is best to use the largest diameter you can in order to produce as large a wound as you can. The United States went from a .45 to a slightly higher velocity .355 lead round (whaich would have had a greater chance of expanding) and found it inadiquate - they then returned to the .45 and jacketed it, like all semi-automatic pistol bullets of the day, not necessarily for military use, but for reliable feeding in the mechanism and, due to higher velocities, less metal fouling of the bore.
In a rather alarming trend the rise of body armor has cause weapons designers to design bullets which skirt the Hague conventions. This is because the armor is easily pierced by rounds designed as armor piercing (which have been around for about a century); however they also glide through the person inside doing minimal damage (especailly since the calibers used now are small). It is not that these armor piercers don't tumble - they do. But, because they are generally soft coated hard metal, they do not fragment like soft-metal core bullets. To make up for this designers have designed bullets with cores that bend once they tumble. This means that rather than stablizing in a "base-first" condition as the old bullets would they continue to twist and hook their way through a body. Unfortunately they are completely "Hague Legal" as they do not expand or fragment.
