The design doesn't take well to dry firing,,I don't recomend dry firing any firearm anyway.

You can let the firing pin down and release the tension on the FP if you want to on an EMPTY chamber by simply easing the toggle forward till it is nearly closed.
About 1/8" before it's completely closed you'll feel a slight resistance,,that is the sear bar engaging the firing pin in preparation to cocking it.
At that point still holding the toggle steady,,,pull the trigger and hold it back. Then ease the toggle to the full down position.
The pistol is now toggle/breech closed,,firing pin down,,chamber empty.

That hesitation holding the toggle in place while you hold the trigger to the rear allowed the firing pin to ride by the sear and miss engaging it to cock the firing pin.

Good info on the MecGar magazines. I use them in several of my Lugers of different vintage and they always seem to function well.
The mag spring in them is powerful and for me at least it is difficult to load more than 5 rds in them,,might just be Mr Arthuritis showing.
The 'skate key' works well when loading the mag.

I have yet to find a Luger incl an Artillery that wouldn't function nicely with nothing but Rem/UMC 115gr FMJ. That is if the pistol is in good mechanical shape, properly fitted, exc magazine, ect. Even a couple of my mixed number put-togethers work fine with the stuff.
Some others use the W/W 'White Box' 9mm FMJ often sold at Wallyworld and the like for their standard.
It doesn't take a special Luger Load of some high pressure, special bullet design and mystic power to make these work.

Changing springs is OK if they need it. I can thruthfully say I've only ever changed the coil mainspring on a Luger twice as I doubted their originality and strength. That's not much in over 40yrs of doing this stuff.
They sell or at least used to sell Xtra Power mainsprings for the Luger. Why I could never figure out. It's not a pistol to magnumize.
The Xtra spring did come in handy one time though in the building of a cut-down Luger we did in a shop I worked in. The shortened grip made less room for the mainspring length.
The Xtra power spring, shortened,, was the ticket to get the normal spring action needed yet fit into the smaller space,,worked well.

The other is the firing pin spring,,it's strength can be judged quite easy by backing out the FP spring retainer(use your 'Skate Key!) and seeing the length of the spring as it sits in the breech and judging the strength needed to reinstall.
Extractor kinda the same thing,,just lift it up,,can tell you right away if it's weak or not (it's a fairly strong little spring too.. Poor extraction will be another clue.