I had a few minutes to check a new spot and I found this rimfire cartridge about 5-6 inches down. I measured and the outside diameter is about 0.46 inches just above the rim, and it is 0.83 inches long. I figure that it is probably 44 caliber. It says L&K on the bottom. Does anyone have an idea as to how old it is and what type of gun it was used for?