As you all know, South Vietnam forces cannot use primary weapons in tunnels, just the pistol. For longer and heavier weapons this is completely reasonable and works well in making the tunnels a hostile environment for US soldiers. However, not all guns in the US arsenal are too heavy and cumbersome to be used in a tunnel, the M3A1 (especially with the folded stock) and perhaps the stakeout variant of the shotgun stand out as pretty compact, so why not use them in a tunnel?
I think its a perfectly reasonable choice for an US soldier to use an SMG in the same CQB environment as a pistol. This might at least encourage people to fold the stock which is a nice but not very popular feature.
I doubt this would at all affect balance since US soldiers don't venture into tunnels very often, and only a few have grease guns with them.
The stakeout riot shotgun variant might also be included for this.
I think its a perfectly reasonable choice for an US soldier to use an SMG in the same CQB environment as a pistol. This might at least encourage people to fold the stock which is a nice but not very popular feature.
I doubt this would at all affect balance since US soldiers don't venture into tunnels very often, and only a few have grease guns with them.
The stakeout riot shotgun variant might also be included for this.