22 rds for a 155 seems okay. But it depends on the type of mission. The old M113 SP mortar carried 55-60 rds like the old 21 SA mortarmen told me. But mortar fire as compared to 155 howitzer is more inaccurate, so they depend on volume of fire to bracket a target...its a cost-effective area weapon IMHO.
155 shots tend to be more accurate, thanks to technological developments over the years...weather ballons, air density, humidity, etc etc....all that Firefinder (24 SA) jazz that no one understands....

With the typical missions that the Primus would face, 22 rds would be sufficient, especially when ammo trains follow them around anyway.
Arty missions vary. So it depends on whether the mission requires sustained fire support, and if so, there has to be ammo carriers nearby. (btw, they do use BV206/Bronco for ammo and POL). But most missions that these SP guns/mortars usually do, are the typical shoot and scoot types...that's what those 21 SA guys told me...so the max would be about 2-3 shots before having to move again; that's their SOP. And they moved around ALOT from one location to another after firing a shot or two; it gets dizzying after awhile for them, racing up and down Area D. For them, their vehicle is their biggest chance of survival in a counterbattery attack, so basically they do everything within the confines of the vehicle during operational mode.
Apparently the person who suffers the most in the SP vehicle is the layer, or simply known as the No. 2 man, since he has to stay with the gun/mortar 24/7 in case of fire missions...lol

...I think I'll go nuts staying in such a confined space for an extended period of time...gimme the freedom of a scrambler anyday!!!
