FYI: Latest on the railgun, which is likely about to go on its first shipboard deployment - please note that many of your concerns have been addressed: https://nationalinterest.org/blog/buzz/fire-us-navys-railgun-may-soon-see-testing-real-warship-59567
I would point out that the Marines only wanted the increased range because the Navy had put all the battleships out to pasture and they needed the longer range fire support. Also, the LRLAP projectile the AGS was to fire was originally to be a joint project with the *Army*.
What’s really embarrassing is that the Russians currently have their various albeit more specialized counterparts to the LRLAP actually already working and issued. The 2A88 152mm gun mounted on the 2S35 Koalitsiya-SV has a *demonstrated* range of up to 80 kilometers using precision guided rounds and up to 40km for conventional munitions. For comparison, our 155mm M109A6 has a range of 24km for most rounds and a 30km range with assisted/base bleed rounds. Even with the special M982 Excalibur rounds it has a maximum range of 40km.
We have developed 52 caliber gun tubes for the M777 and the M109A7 but again greater range absolutely requires guided munitions and Quarter-Million Dollars a Pop rounds.
When I was doing this stuff, we designed our own system in-house at Picatinny Arsenal, built it a Rock Island, and tested it at Yuma - and our direction was greater automation, faster rates of fire, high ballistic precision, and fire on the move. I guess we'll see where the technology takes us.