School me on Saiga 12s. I definitely want one, will mostly be using it for skeet and 3-gun shoots, so I am leaning to the 24". But I heard the 24" barrel only have 2 gas ports instead of 3. Does that affect reliability with lighter loads? Thanks.

19" is better suited to Tactical use, while the 24" is better suited to hunting/sporting use.
There really is no "all purpose" shot gun. You should really have a short barrel and long barrel.

Get a 19" first.

My 24" had 3 ports. Now it's my 18.25"

Are they easy to swap out? How much does a new barrel cost? Thx.

I run a 19" for 3-gun and it gets the job done. (There's a video on the first page of this forum)

I'd get the shorter barrel, mine works fine but I haven't tried skeet with it except for hand-thrown or single fliers activated during a stage.

All s-12's are supposed to have 4 gas ports, you can bend a paper clip at a 90 degree angle and feel inside the gas block for them and they should be in a diamond pattern.

If you have three ports and a good piston to bore fit you might be ok for most low brass, if you have only 2- highly unlikely to cycle low brass.

The barrels are pressed and pinned in place, Alliance has and can make new barrels but you will most likely never wear one out so why make them? Here's a hint- if you let a gunsmith or anyone else remove the barrel or gas block to port the barrel make darn shure they support the barrel internally with a steel slip fit mandrel and use a hydraulic press with fixturing to support the receiver as well, some s-12 barrels press out with ease and others dont, either way you can damage the barrel very quickly and I would also advise you get in writing what their "performance service" is going to do i.e. will it reliably fire low brass and or a specific brand of ammo.

I've got both a 19" and a 24" S-12.  Get a 19".

19 it is! Yeah that Atlanta competition shooter is pretty amazing with it.