I think I'm uniquely qualified to answer this question since I am a former Field Artillery Officer. I've fired thousands of rounds from both a M109 Self Propelled Howitzer, but more importantly, an M110A2 eight inch self-propelled howitzer. The 8" was the biggest howitzer ever in NATO's arsenal and I was in an 8" battallion for 6 years. I loved those things, unfortunately, they were taken out of the inventory in the early to mid 90's. They were very accurate and you just could not believe what those rounds sounded, or rather felt like. I practically get wood thinking about it. When you shot a round and it exploded anywhere from 30 seconds to 3 minutes later, depending on the range to the target, it sounded and felt louder than thunder. Imagine 98 pounds of TNT exploding 10 miles away and being able to feel it. It was awesome! I'll have to upload some pictures some day to show you guys. I have a picture of my wife pulling the lanyard on one of those big boys with the tube in full recoil of about six feet.
Thanks for the memories and flashbacks!