Well, here’s a pretty pic. I think I heard URR squee all the way across the country.
#USArmy Soldiers, assigned to 3rd Brigade Combat Team, 4th Infantry Division (Iron Brigade), fire a M109A6 Paladin self-propelled howitzer at Udari Range Complex, Camp Buehring, Kuwait Mar. 12, 2015.
U.S. Army Photo by Maj. Gene Palka
The M109 is, of course, primarily an indirect fire weapon, used to support the direct fires of maneuver forces. On occasion, however, they might be called upon to deliver direct fires. That’s usually a very bad thing, having to fight for the guns, as it were.
As such, it certainly makes sense to train for it from time to time. Plus, it’s fun to watch big shells go boom at a relatively close range.
The US doesn’t issue anti-tank rounds for its howitzers, but the Soviets did. Typically, two or three HEAT rounds would be included in the basic load of a Soviet howitzer.
The rule of thumb for HEAT round penetration is diameter of the round, multiplied by six, is the rough equivalent in RHA. So a six inch (152mm) round should have a penetration of about 36″ of RHA. Not many tanks can handle that.
Of course, direct fire in a howitzer is pretty short. Like, around 1000m. Tanks have a somewhat longer effective range.