Question: Infantry vs Artillery

[Warmonger]

For the first time I had infantry engage artillery units. As a result there were a number of remarkable incidents.

The artillery were in a series of clearings surrounded by woods. They consisted of numerous 105mm and 75mm howitzers and 80mm mortars. The artillery were noted by smoke when they fired. It took a long time (30 turns) for the infantry to work their way to the artillery having to defeat some protecting forces on the way.

When the first infantry unit got to the edge of the first clearing it spotted a 105mm 8 hexes away. It fired its primary weapon, rifles, at the artillery. A message came out that the 105 was destroyed.

Question: is it reasonable long range rifle fire could destroy a large gun like the 105?

The 8 man crew was apparently destroyed as well. I've seen multiple hits but never 8 at once, especially at long range.

The artillery units had their gun as a primary weapon and rifles as secondary. As the action went on I noted that almost none of the artillery fired their rifles. The infantry were able to move adjacent to each unit and blast them. Of 12 105s one fired both its main gun and rifles; of 12 75s 2 fired their rifles; of 9 mortars 4 fired their rifles.

Since this was late in the game I'm guessing most of the main guns were out of ammo. But should this influence firing their secondary weapons? Or is there something else which would cause this kind of behavior?