Note of caution. It seems unlikely given the rarity of the .455 Automatic cartridge, but do NOT fire them in a .455 revolver. They will work because the .455 Auto is semi-rimmed, but the pressure is a lot higher than .455 revolvers were designed for. The British War Department put out a notice on the subject at one time.
On much the same subject, if you have one of those .455 Webleys (Mks I-VI) that were converted to use .45 ACP with moon clips, DO NOT fire standard or mil spec .45 ACP or any heavier .45 ACP load in it. Some of those guns have blown with normal .45 ACP GI ammo. In spite of the Webley lovers, even the Mk VI is not the strongest revolver in the world or anywhere near it. So don't blow one of those old timers trying to prove it is.
Also, the often-made statement that the Colt autos made for the .455 Auto are identical to the .45 ACP gun. Not true, even the frames are different to take the wider magazines, and barrels and slides are different.