"Some guns were chambered for .22 ILARCO ammunition, also known as .22 Short Magnum rimfire, as it was a .22WMR (Winchester Magnum Rimfire) cartridge shortened to the same length as .22LR cartridge"
Sounds a lot like the Winchester .22 Winchester Rimfire Automatic, that was used only in Winchester's Model 1903 semi-automatic carbine. Or the .22 Winchester Rimfire, that was the parent cartridge for the .22 Magnum.
.22 Winchester Automatic Rimfire (WRA or WAR):
Bullet diameter . . .222 in (5.6 mm)
Neck diameter . . .250 in (6.4 mm)
Base diameter . . .250 in (6.4 mm)
Rim diameter . . . .310 in (7.9 mm)
Case length . . . .665 in (16.9 mm)
Overall length . . .915 in (23.2 mm
.22 Winchester Rimfire (.22 WRF):
Bullet diameter . . . . .224 in (5.7 mm)
Neck diameter . . . . .242 in (6.1 mm)
Base diameter . . . . .242 in (6.1 mm)
Rim diameter . . . . . .294 in (7.5 mm)
Rim thickness . . . . .050 in (1.3 mm)
Case length . . . . . .965 in (24.5 mm)
Overall length . . . 1.180 in (30.0 mm)
.22 Long Rifle (.22 LR):
Bullet diameter . . . . .223 in (5.7 mm)
Neck diameter . . . . .226 in (5.7 mm)
Base diameter . . . . .226 in (5.7 mm)
Rim diameter . . . . . .278 in (7.1 mm)
Rim thickness . . . . .043 in (1.1 mm)
Case length . . . . . .613 in (15.6 mm)
Overall length . . . 1.000 in (25.4 mm)
.22 ILARCO:
No data available