Complex sentence: It was test fired at the Frankfort Arsenal at Philadelphia in 1880 and was proven unsuccessful; due to faulty obturation, the flash from the original propellant charge bypassed the projectile and prematurely ignited the subsidiary charges before the shell passed them, slowing the shell down.
Split into simpler sentences: It was test fired at the Frankfort Arsenal at Philadelphia in 1880 and was proven unsuccessful. Due to faulty obturation, the flash from the original propellant charge bypassed the projectile and prematurely ignited the subsidiary charges before the shell passed them, slowing the shell down.