Morning Captian,

The 455 Webley cartridge is of larger diameter than the 45 ACP. When 45 ACP ammo is fired in converted Webley revolvers, the cases bulge. They are then either split or so large as to be unusable.

The conversion was popular when 455 Webley ammunition was difficult to obtain and 45 ACP hardball was common. Hornady makes 455 Webley brass; at Graf & Sons it costs $30 per 100.

Take care, Tom