Hello.  Because of their perfect diameter and the shape of the cold formed head, some Masonary Nails I found should yield perfect prototypes of an (eventual) wire form component for a new product.  But just one catch.. How to I slightly "soften" them to put in a few tight 180° bends, but then harden? - temper?? them back up to "full strength".  Thanks!

To "soften" the metal, are you talking about annealing them? It depends on what they're made out of. Some metals, if you heat them and let them slowly cool, will be softer/easier to work with. However, there are metals out there that will "air harden" if you try that. Or if you have a torch you can attempt to heat up the area you want to bend until it glows at least red, and then bend in a vice or a jig. However, the best bet is to know what the material you're working with is, and research it's properties that way. That way you will also know how to harden them (what I'm assuming you mean by "full strength") and temper to reduce stress so whatever function you are going to utilize them in won't cause failure in the material.

Welcome to IFI... I suggest reading this thread to get the best out of the forum. READ THIS FIRST  some answers depend upon your location, hence the suggestion to edit your profile to show location.

I would suggest bending them hot and then heat treating them appropriately.

You'd need to talk the manufacturer of the nails you have in hand and see if they'll give up their propriatary information to you.

You want to put a COUPLE 180* bends in a masonry nail? As Thomas says that's hot work. Please post a pic, considering the dia to length ratio I'm having trouble visualizing two 180* bends being anything but folded closed. 

I believe you'll have better results buying high carbon steel wire you can work and heat treat appropriately. 

Frosty The Lucky.

I agree with Frosty, make your own nails from known steel.

Bend them hot, which is likely the only way they will bend anyways, then use them as is, they will still be plenty tough.