Yup its quite different at Crossfire. If I'm not wrong, the playing area is like a maze of sorts and the paintballs used are smaller too.
There are regular paintball markers modeled after real life guns to cater to the military simulation/woodsball crowd. A very popular one is the Tippman A-5 which has all sorts of add-ons to make it look like some of the most popular rifles/SMGs out there.
Funny you should mention about "zero-ing". Unfortunately, paintball markers are not exactly very accurate things. There are many factors, but the two main factors are that one, the propellent is compressed C02 or air, so there isn't much force and two, paintballs are very light. They are liquid paint in gelatin capsules so wind and humidity affect how accurately they are fired from the marker.
Heckler&Koch, if you're keen, do join in the paintball outing I will be planning soon. I think you will have more fun playing at Red Dynasty. Cheers.