
The .17 HMR, and it's little brother the .17 HM2, are rimfire cartridges like .22 magnum and .22 long rifle, necked down to .17 caliber. You can read more about them here and here if you're interested. My thoughts however have revolved around the idea of using them as scale empties in dioramas. The dimensions aren't perfect, the .17 HMR works out as more of a 5.5" (140mm) diameter shell in 1:32, and the empty case would stand 34" inches tall, with the .17 HM2 being shorter. So as you can see, they don't really match up with any common shells, but, they look so dang good being actual brass, hollow, and usually with some firing residue on them, that I think I'm willing to use them anyway. I doubt anyone will actually be measuring them anyway.
Now of course, for the downside. I model mostly modern, and modern tanks aren't known for using big brass cases. But still, I just had to have a few of these to scatter about...
MV