GPS fuze, guidance systems, actuators, battery, ramjet, fuel, fuel pump .... this begs the question how much weight and volume inside the shell will be left over for the actual explosives ...
@candydale45 - Get a shot accurate enough and you might not always need explosives.
I think shoulder-fired missiles could also benefit from ramjet tech for increased range!
I find it interesting that there is always money for the big MIC companies, but there is never money to help the individuals or the small businesses. In fact, now that we are using an alleged pandemic to shut down most of society, only big government and big business seem to be benfiting from the unconstitutional lock-down. Sad, don't you think?
I recall that, back in the fifties or sixties, the Army was testing solid-rocket boosted shells to be launched from artillery tubes.

What goes around, comes around...
Expanded Viewpoint
Way back in the day, when I was the machinist for the rocket club I was in, I was told that loading a 600Lb chunk of concrete, minus any rebar as a warhead in a V-2 rocket instead of Amatol, would do almost as much damage upon impact! The kinetic energy of the concrete falling from altitude, with the fragmentation of it upon landing and throwing shards of sharp rocks everywhere would be devastatingly effective. The sudden injection of that massive amount of energy into the ground would shake buildings for hundreds of yards in all directions, and direct hits would knock most of them down. But companies make more profits by selling explosives for bombs than they do concrete.
Gerald Vincent Bull's modification managed the same results.
Expanded Viewpoint
Highlander, it's because ALL wars are banker's wars, so they "invest" their phony electronic bookkeeping entries where they will get the most return! Wars beget more wars, and lots of hidden profits. Peace begets more peace, but the monetary profits are not as high and are easily seen by all.
Robert Craigs
to HighlanderJuan: While I also consider it sad that the MIC gets s high proportion of the GNP, I can't accept your 'alleged pandemic' without comment. LOOK AROUND YOU. I have a friend in an extended care home. He, so fa,r has survived a Covid 19 Infection. The American Constitution doesn't just cover your RIGHTS. One of your responsibilities is to defend the country when it is necessary. The so called lockdown is a way to defend your country from a serious threat.
I wonder how much longer this round is and if it is more expensive than simply launching rockets from a launch tube. I thought the 155mm only had a range of about 18 miles. I was in an artillery unit with the larger 8 inch self propelled guns with a range of a little over 21 miles with a 100 pound projectile. We also fired 300 pound nuclear simulators but the range was only about 12 miles. Way too close to ever want to use them in battle.