Hmm.
Well the idea here is to use the "first stage" 357 ignition to light off the "rocket". Maybe the way to do that is with a fuse! Instead of filling the 32 primer pocket with Unique or something, pour grains of powder onto some...I dunno, toilet paper, twist it up, and run it through the 32 shell's primer pocket hole into the 32 shell main charge. Or...hmmm...powder can be formed into a solid, by mixing well with a combustable liquid and allowing it to dry? Fill the 32 primer pocket with that, with the "powder paste" run right through the 32's primer pocket hole before it dries. That should form a predictable "fuse" that would burn away just as it lights the rocket. Different burn speed powders used in such a paste would let you control the "fuse speed" to some degree. For best results, you want the rocket to kick in just after it clears muzzle. Too early and you get a pressure spike from hell
. Methinks we oughta test this in a Blackhawk, or one of Weshoot2's Redhawk .357s
.
We'd have to experiment with the proper size of the hole in the 32 shell's primer pocket, for maximum thrust.
Another thing: is the .32ACP shell *tapered*!? That would complicate things a bit. The rear end of the shell might be very close to .356/.357, and only the front end of the .32 shell would need "support" of any kind. If you didn't support the front with a ring of...something, tape maybe, the danger would be that the rocket round would come out of the muzzle slightly yawed, and when the rocket thrust kicked in, God only knows where it'd go.
You know, I'll bet we could scale this whole concept up to where we use a .45ACP "second stage rocket" in a .475Linebaugh or .480Ruger "first stage". Jeez, that'd be completely off-scale nutso
.