It does sound like artillery, but it could also be an anti-tank gun. While explosions in modern artillery (basically since the advent of breech loading weapons) are rare, they do happen. For example, "separate loading ammunition" (normally 155mm and bigger) consists of a projectile that is rammed into the breech (the lands bite into a copper band to prevent it from sliding back) and bags of propellant are placed behind it prior to the breech being closed. Following the firing of the round, a sponge on pole (the swab) is used to wet the inside of the breech to ensure that the embers are extinguished be throwing more bags of propellant inside (just like in the muzzle loading days of yore). If this is not done, there could be catastrophic events. There is also the possibility of overloading the breech or even the explosion of the round upon firing. This could be caused by a breech obstruction or faulty ammo which I would think may be more prevalent in days when ammo was hurriedly manufactured and shipped like in WWII. If you will recall, 7 Marines were killed when a mortar was fired after being double loaded.
Here are some arty loading pictures:
The Projectile ram -
The propellant (this one isn't made up of bags, but one solid container)
About to swab a M777 155mm gun:
