An Australian company called Rimfire Research are developing a range of front locking rimfire rifles.
Two rifle actions are being developed. The short action will be built around the .22 LR cartridge and the long action around the .22 Magnum. The bolts will be the minimum size needed to accommodate these cartridges. They will feature three front locking lugs, mechanical ejection and controlled round feed.
Apparently many years ago Mauser produced a front locking .22 rifle, as did a Russian firm, although neither produced them in much quantity.
[ Many thanks to Mehul for emailing me the link. ]