The first issue you'll face is the probability that the explosive charges won't be aligned. One goes off a millisecond before the other, and it'll go flying off to one side due to one side moving faster than the other. For a bullet moving the speed of sound, it'll move 13 inches every millisecond.

You could time the charges better by connecting them with with a shared high-explosive fuse, but then you'd have to connect the insides of the barrels. You'd probably want to for the cord in any case. Otherwise, you'd have the cord running through the barrels, and that would be bad.

For separation, here's a fun sci-fi-ish possibility: Make the cord out of memory-wire that reverts to its original shape when heated. It wouldn't need to snap into a solid bar, it would just have to act like a spring.

Alternate possibility: secondary charge. The wire is coiled up between the two bullets. Have the shared fuse also light a slower fuse that blows a tiny secondary charge, wrapped in those coils. Not enough to damage the wire, but enough to push the bullets apart. You'd need to optimize it for a specific range because the bullets would have a tendency rebound back into each other.

Yea, monomolecular wire isn't a real thing right now, but science is funny. They keep finding things that change the paradigm, like lithium-sulfur batteries or new phases of matter. Admittedly, this would be on scale with something that you could build a space elevator out of, but it downgrades the idea from "impossible" to "implausable," and that's enough if you wrap a good story around it.

The first issue you'll face is the probability that the explosive charges won't be aligned. One goes off a millisecond before the other, and it'll go flying off to one side due to one side pulling on the other. For a bullet moving the speed of sound, it'll move 13 inches every millisecond.

You could time the charges better by connecting them with with a shared high-explosive fuse, but then you'd have to connect the insides of the barrels. You'd probably want to for the cord in any case. Otherwise, you'd have the cord running through the barrels, and that would be bad.

For separation, here's a fun sci-fi-ish possibility: Make the cord out of memory-wire that reverts to its original shape when heated. It wouldn't need to snap into a solid bar, it would just have to act like a spring.

Alternate possibility: secondary charge. The wire is coiled up between the two bullets. Have the shared fuse also light a slower fuse that blows a tiny secondary charge, wrapped in those coils. Not enough to damage the wire, but enough to push the bullets apart. You'd need to optimize it for a specific range because the bullets would have a tendency rebound back into each other.

Yea, monomolecular wire isn't a real thing right now, but science is funny. They keep finding things that change the paradigm, like lithium-sulfur batteries or new phases of matter. Admittedly, this would be on scale with something that you could build a space elevator out of, but it downgrades the idea from "impossible" to "implausable," and that's enough if you wrap a good story around it.