BSA also made their 'Garden guns' up until the mid 1920s on enfield actions. I picked one up in gunbroker for about $200 6 months ago. Chamber needs to be cleaned before it will easily chambe. Modern .410 cartridge though but it's perfect for squirrels etc etc (or will be).
I have two of the ishapore No.1 410 shotguns but I am fairly convinced that both were made to that spec new in ishapore as opposed to converted. Both are chambered for 2 3/4" shells.