US Military's M110 (Self-Propelled Howitzer)

Replying to @PakMann69 Iran likely still makes 203mm shells, as evidenced by reports of supplying them to Russia and its indigenous production of artillery, which includes systems that use this caliber. Iran has the necessary artillery, such as the M110 self-propelled gun and M115 towed howitzer, to utilize 203mm shells, and has established a domestic arms industry. Russia makes 203mm shells, though its ability to produce them domestically may be insufficient, as it has reportedly imported shell

Evolution of U.S. Artillery & Rocket Systems (1942–2020) From M7 Priest to XM1299 ERCA Cinematic