The IDPA 5×5 Classifier was introduced not long ago as a way for competitors (and ranges) to quickly get competitors through the classification process. The original Classifier Match (which is still available for IDPA members, if they can find a club that uses it) is considerably longer, requires more range equipment (and more range space), tests more skills, and requires significantly more ammunition. Unsurprisingly, lots of local clubs have shifted to using the 5×5 classifier for their members instead.
The entirety of the 5×5 classifier is shot at a single IDPA target at 10 yards. It consists of 4 strings, taking a total of 25 rounds to finish the course of fire. Concealment is NOT required, and it is Limited scoring, so be sure to ONLY shoot exactly what the stage briefing specifies.
If you want to be completely prepared to shoot the 5×5, you should come to the line with a holstered gun and at least one mag pouch (for the one on-the-clock reload that is required), no concealment garment, and 5 magazines, one of which is loaded to exactly 4 rounds. If you do that, you will simply reload to a new magazine on every string, making sure that you start string 3 with the magazine that only has 4 rounds in it. (After the first string, you’ll always have one round left in the chamber when you load for the next string, so that gives you five rounds at the start of string 3.)
If you don’t have enough magazines to load a new one each time, you can get away with not reloading between strings 1 and 2, and also 3 and 4, IF you are allowed a magazine capacity of 10. If not—you need to reload to a new magazine between each string. If you don’t have five magazines, have a friend stand behind the firing line, and hand mags back to them so they can reload them for you while you shoot.
As you can see, you need to be able to shoot freestyle, shoot strong-hand-only, and be able to perform a slide-lock reload on the clock. Oh, and hit a headshot at 10 yards on the first try, as no makeup shots are allowed.
And yes, you CAN ask the SO between strings of fire what you are supposed to be doing for the next string–that’s perfectly legal.
Good luck on your classifier run!