My first carbine match is on Sunday, please help!

I'm having some trouble with my DSA STG58a carbine. It doesn't eject the empties, in fact it doesn't seem to extract them either. Here's the info I have from playing with it, breaking it down, and so forth. It was working fine last time, and I keep it clean.

1) The first shot from any magazine works just fine. Shoots straight, one shot.

2) The bolt freezes about 1cm down, with the casing in the claw. The handle is jammed, and usually requires being braced to unstick, at which point the casing will eject normally if I work the handle fast enough. Otherwise it just drops in the well, as expected.

3) Cycling the action with the handle will feed and eject normally, all innards appear to function normally. No signs of unusual wear or metal on metal, and the action is lightly lubed with CLP.

4) The gas port is set to 5, the ammunition is surplus Port in the vinyl battlepacks, that the gun usually is fed. It functioned flawlessly last time on this same ammo, same settings.

5) Tested four of six magazines, different types, all from Tapco. I should have tried all six, but I got hot and frustrated, and called it a day.

Any suggestions? I was hoping to shoot at the carbine match this Sunday... doesn't look like this is gonna happen now.

Check the recoil spring in the stock. You may have to compare to a new set to see if they are compacted.

Sounds like you need to tighten up the gas setting.  I know you've used it at 5 before, but the symptoms you describe are typical of not having enough gas to operate the action.  Your description of the force required to clear it is also typical of this.  In the future, do the FAL pogo.  The pogo means smacking the butt of the gun on the floor using your right hand while your left hand cycles the charging handle.  It works every time.