with the .310 Cadet cartridge. I've written about it before, so to give a review:
Unless you've got a lot of money free, it's a roll-your-own.
Form it from .32-20.
Uses a heeled bullet. Which means externally lubed.
Now, the heeled bullet part is the original design, but- depending on the actual bore diameter of a rifle- you may be able to use standard bullets. The one in question has worked with some, in particular a SWC designed for .32 Long when cast of a fairly soft alloy.
At one time, during WWII, the Aussies made this cartridge with a jacketed pointed bullet for use by their 'the Japanese might invade, and we'll need EVERYONE, so we need bullets that are approved by the Convention for these rifles' home guard. One or two companies still make them, but they're in Australia which makes getting any problematic.
I had a thought:
X-Treme makes a copper-plated 123-grain bullet for 7.62x39*, which I've used with success in several cartridges. It's a nominal .311" diameter, but I wondered if it would work in a tighter Cadet bore, or would upset enough to shoot at least decently. So I loaded some up. Some, loaded with Unique, I seated the bullets deep enough that the base was a deep into the case as the heel of the original bullet; some with 2400 were just a touch deeper. Five rounds of each at 30 yards, the Unique loads on top
*They're out of stock right now, so no picture on the site. I'll take a picture of some and add it later.