This is a sad procurement story for sure. The use of existing 155 mm rounds should have been part of the contract even at degraded performance. IDK, maybe the Army put a strangle hold on its stockpile. I wonder if there were hearings on the Hill on this. Had to be.
From wiki: "Shortly after the USS Zumwalt (DDG-1000) was commissioned, the U.S. Navy moved to cancel the LRLAP due to excessive cost overruns. With the number of ships reduced from 32 to 3 examples, the per-unit cost of each LRLAP shot increased to $800,000-$1 million. This made the system untenable despite no significant performance issues. Other projectiles are being examined to replace the LRLAP, but since it is the only munition designed to be fired from the AGS, the barrel, software, cooling system, and automated magazines would have to be modified to accommodate a different round. It is not likely an LRLAP replacement could be put into service by the time Zumwalt enters operational service in 2018. It could cost up to $250 million in engineering costs to modify all six guns on the three ships to accept a new round."