I've been messing with small capacity and small caliber wildcats for a while, and the most recent endeavor is the .22 ladybug. It's intended to answer the question of "Is there a direct CF reloadable replacement for the .22 LR?". While the ladybug requires a different chamber than the .22 LR (experiments for a cartridge that didn't require rechamber didn't go well) it is a very good analog for the .22 LR cartridge, performance will be discussed below.
It ends up being pretty similar to the cartridge Chas. Askins developed in the 30's (the .221 askins) though it's derived differently and has some dimensional and application differences.
Beside the LR cartridge:
I was explaining to my wife that many small caliber wildcats are named after bugs, like the hornet, bee, wasp etc. She said this one is more like a ladybug "It's cute, and it kills garden pests quietly". So the name stuck.
Here's the ladybug next to a few behemoth cartridges, the .32 S&W long and .32-20.
So far I have 2 rifles in the caliber, a 16.25" Contender (easiest conversion ever!) and a 24" H&A falling block. All accuracy and velocity testing has been through the contender.
Case capacity is fairly low at avg 3.91 grains water capacity. As a result, powder charges are low. I'm currently experimenting with titegroup powder, as it's very conducive to the small capacity and bore of the cartridge. 1.1 grains of TG is pushing a 40 grain cast bullet (BHN 12-13) tumble lubed with 45-45-10 to velocities of 940 FPS avg. (keeping it subsonic for suppressor use).
The first 10 shot (offhand) group at 25 yards with that load:
I've pushed the same bullet as high as 1600 FPS, but at those velocities, the accuracy was terrible and it loosened the primer pockets in the brass and stuck brass in the chamber. Loads up to about 1250 FPS remain accurate and show no pressure signs. This is intended as a .22lr replacement anyways, so keeping things below about 1250 doesn't give up anything on the desired goals of the cartridge.
I've also tested a light bullet through the gun... you know, for the recoil sensitive... at 20 grains, the same 1.1 grain TG load pushes it close to 1300 FPS, but maintains accuracy.
I started out making brass from .22 hornet brass through a fairly complex process and a number of operations on the lathe. I later realized that I could accomplish the same thing by using cheaper brass, I just couldn't have the length any longer than the original RF case. After several iterations, I arrived at the current version.
Now I form the ladybug from .25ACP brass. I deprime the brass first, then using a special base punch designed to support the primer pocket, I swage the body down in 2 steps from .278 to .247. I swage all the way to the rim, but the brass springs back more around the web of the case, so I still have to do a quick trim in the lathe just above the rim, although I'm only removing about .003 from each side, and not touching the original rim.
The brass ends at .247 diameter straight, with a rim diameter of around .300-.305 and thckness of .042. My chamber is .251 straight with a rim recess .309 in diameter.. trim length is .625" and long bullets can theoretically be loaded and fired due to the long throat that results from the rechamber from the .22LR chamber, but I haven't checked anything over 45 grains for stability.
The first 10 cases I made are still going strong without even an anneal, and they've all been loaded and fired at least 50 times. I just dump them in the ultrasonic for a bit between loadings to remove the powder residue.
I've made up a bunch more brass, and I'm working on a way to make the brass without a trip to the lathe, but I'm not 100% happy with that solution yet.
Here's a box of ammo ready to go shooting: