Ok these have been baffling me for a while. I picked up a small box of about 90 these in an estate sale earlier this year, so far I can't find any info on the interwebs about these. These are based off 307 Winchester cases with an over all case length of 1.59", base of shoulder to case head is 1.20", case mouth is ~.280" (not sure if they are sized or not). I took a picture of them next to a 30-30 Win case for size comparison.