The 1st attempt to replace the Sheridan, - the M8 Armored Gun System[0] had a similar problem - too heavy to be transported / airdropped by a C-130.<p>[0] <a href="https://en.wikipedia.org/wiki/M8_armored_gun_system" rel="nofollow">https://en.wikipedia.org/wiki/M8_armored_gun_system</a>