Shotgun too! You need all 4 guns. The "3 Gun" part of the name refers to 3 different types of guns. Not 3 guns only.
It's quite a bit different from SASS/NCOWS style matches. Scoring is done on the IPSC hit factor basis. Points are earned by hitting targets. More points for a center hit.
Penalties for misses and procedurals are 10 points deducted.
You can move while shooting, but you must maintain trigger discipline. You can also move with a loaded gun and hammer back (includes shotgun), but you must maintain trigger and muzzle control. Remove your finger from the trigger gaurd until ready to shoot.
Empty's left on the carrier or in the gun are a no call, and yes that means for SxS's too!
You can reload and pick up misses, sometimes with a different gun. I missed a pistol shot and picked it up later with the rifle on one of the stages.
Prizes reward performance, instead of delivered on a random basis. The better you do, the better your prize! There might even be cash handed out at future matches.
Stages are designed for action. There will always be some that require movement in order to see and engage targets. For example, you might get off 3 pistol shots and then have to move to see another target before firing the other 2.
This is a very high paced shooting game, with an accuracy component.
For example.... (just using pistols as an example):
You blow through 10 shots in 5 seconds and don't hit any center. That's 30 points/5 seconds or a hit factor of 6. Or, you back off a little, shoot it in 8 seconds, and get all the center hits. That's 50 points/8 seconds or a hit factor of 6.25. That wins.
Hope this helps.
Doc