The shoulder on the on the right reminds me of PVFM (or something like that) cartridges. Also, it seems to me that there’s an old one with a similar shoulder that I’ve seen in an old reference book. If I find it I’ll send you the information.
They both could be Epps cartridges. Epps owned a gun store in Canada and he came up with a whole family of cartridges based on the .303, from .22 up to .28 caliber and at least up to .35 caliber.
I just did a search of “Epps cartridges” and one of the options that I chose was “Images of Epps cartridges” (do not include the " mark). There were two photos that look like the one in your photos, on the left side.
I found that several of Epps’ cartridges now have other names like .40-65.
I also went to Elwood Epps’ website. I didn’t find anything with Epps’ cartridges, but several years ago I thought of making runs of Contender barrels in various calibers, so I called them. I’m sure that if you gave them a call they’d be happy to talk to you. My biggest problem is that I ended up spending an hour on their website! Oh, the guns they have!!!
There was also a .303 Epps that was about the same as Ackley’s cartridge.
The RCBS site lists one or more sets of dies for Epps’ cartridges.