If by "truck gun" you mean a self defense gun, the Sigma will do just fine. Buy a box or two of ball ammo, hang a paper plate out at 3-7 yards, and see if you can put every shot on the plate. Go ahead, try 'point and shoot' without aiming, but just pointing it as naturally as you can. Don't think about it, just shoot it. You should find that it works fine in this fashion.
Load it with your choice of ammo, and try a magazine or two, or a box or two, to satisfy yourself that is will feed reliably, then load it and carry it where you need, as you need.
So, as a "truck gun" it should be dead reliable, and you should be pleased.
Ah, go ahead and try some 'run and gun' shooting in the Stock Service Pistol category, and you might just enjoy that too.
Don't over-think it, and don't believe everything you hear or read on the internet...