It's a howitzer. If you can see it, you probably need to back up a bit to shoot it. Everybody in artillery talks about using as a direct fire weapon, much like tankers talk about using the tank cannon as indirect fire (I forget the name of the attachment you use to do this...).

In reality, 38 is fine for a vehicle that is meant to be behind the FLOT. The reason why the M1 has more speed is so it can act a lot like guys on horses: lots of back and forth and attacking quickly and exploiting flanks, etc.