RamscoopRaider
Donor
The range was specifically in the context for Israel. Namely that said gun would in Israel's case be in range of tactical weapons from their neighbors and thus vulnerable to non strategic conventional weaponsI find this argument a bit strange. Land-based missile silos seem to be in a comparable position, yet, we're all quite willing to accept them as part of a triad. The French used MRBMs as part of their deterrence force, so range is obviously not an insuperable problem. You can't hide it or harden it? Well, you can't hide or harden missile silos either - or more to the point, the same techniques used on them will work just as well on a gun if most of the barrel is underground. Yet clearly missile silos were considered to be durable enough to be worthwhile, even in the face of an opposing superpower's arsenal. Arguing that they were a waste of money is possible, but difficult. If we remove the requirement that this be used by a superpower, then it might be possible.
For the record, I'm not asserting that this is superior to SLBMs or TELs rumbling around in a desert somewhere. But that's okay, because all we have to do is find a different nuclear triad, not one that's better. And I don't think a gun is obviously crazy talk - Project HARP test-fired RVs with delicate electronics and they did okay, so delicate systems can survive those sorts of launch stresses.
You can in fact harden a silo, as it only needs a 3 meter or smaller hole for the missile to leave from. The gun needs quite a bit more than that so that it can be brought out and traversed onto the target. Otherwise you are stuck with having to have each gun only dedicated to a band of targets, and realistically you need a cluster of guns for each band of targets as some will not survive the enemy first strike and dealing with mechanical issues. As such Israel, who has to worry about all of its neighbors would need a whole bunch of different gun batteries, or if using a single gun or battery of guns, have to have it be able to traverse, which means a railway gun style turntable system
HARP did it's work in the early to mid 60's, and managed to achieve their electronics shielding at the cost of payload mass, namely them filling the electronics bay with sand and epoxy adding weight, similar to how they eventually got the rocket propellant to survive by filling it with liquid. I'm fairly sure the guidance systems of the time won't work that way, and without guidance the dispersion at that range is too much even with nukes
The issue with HARP type weapons is that they only become viable after missiles exist and you can piggy back off others missile programs easier than developing the gun on your own