Not sure if this is in the right spot, but I think it is a BP cartridge so....
Had my eye on a sported Greener that recently sold on Gbroker. It was listed as being chambered in 40/2.355. I looked all over for any info on that round and even looked at case measurements to try and figure this out. Best I could guess was maybe a .303 Brit necked up to .40 but not certain.
Anyone know what this might have been? Thanks.