Battlefront knows that the US used more than just one type of mortar during the Vietnam conflict. Here’s their look at another type used during the fighting.
From the website:
The M30 4.2in (107mm) mortar first entered service with the United States Army in 1951 as a direct replacement for the M2 107mm mortar. Despite being twice the weight of the M2 (305kg vs. 151kg), the M30 enjoyed greater range and an increase in killing power when compared to its predecessor.
Due to its weight, the M30 was often mounted in vehicles such as the M113 where it could offer mobile fire support to hotspots on the battlefield. When mounted on the ground, the base plate had to be dug-in and covered in sandbags in order to stabilise it. But even with these measures, the recoil caused when the weapon was fired would cause the base plate to shift therefore drastically reducing accuracy. What’s more, rate of fire was also reduced while the crew were forced to recalibrate the sights with the aiming stakes.
In many cases these were discarded for the lighter and more mobile M29 81mm mortar to allow the platoon to accompany the battalion on combat operations.