Like mentioned by a few, writing zeroes and ones or using some wiping program is critical when HDDs are going to change hands. Formatting doesn't really erase the data.
With that said, this was a good and informative topic to address and may keep someone out of a mess of trouble.
I've done that to a few. A nice chisel and hand sledge work VERY well.
If I'm going to toss them, that's the method I use.
I usually do the 10 pass on the drives I feel must be wiped and a hammer on those I consider "critical:.
That has got to make a noise !
There IS this option but it too takes several passes to be effective:
Corrosive,
I thought about using my old drives for targets, too. They'd be great for a 200yd target for a .223 I already had fun with my original Hughesnet dish and my shotgun. LOL. That made a mess to clean up, though.
Corrosive,
I've often thought about that (using the .22LR), but was always a little worried about what the main part of the body of an HDD is made of. Cast aluminum? I was just concerned with ricochet. I have some old 42gr round nose which might actually be perfect for that.
Gary,
Eek! I've got a bad back as it is. I can't imagine what those 12ga magnums feel like. The regular 12ga shell is about all I want to handle, and even then, four or five shots and my shoulder and back are spent. I bet that sucker made a nice mess of that dish, though. LOL.
Corrosive,
I think you previously mentioned that you had servers. I had forgotten about that, but with a server, or servers, I can definitely see a high capacity HDD like that being necessary. For me, if it's not mainly for storage, I go with the SSD, too. Each of my three PCs have Samsung EVO 250GB SSDs. My desktop also has a 500GB HDD in it for storage, and I have the 750GB external USB drive for the backups. I actually still have the original 500GB Laptop HDDs that came in my laptop and notebook, but they just sit there with the original W8 they had on them before I replaced them. I have four 16GB flash drives for transferring files between computers, too, although one has the Windows 10 upgrade files on it.
Thirty days to wipe one of those disks...sheesh!