Some progress has been made!
My Wolff 36# mainspring arrived today so my first step was to replace the original with the Wolff. This Wolff spring is a good 1" longer than the original I replaced. Also, just operating it by hand, it feels tighter/stronger than the original. I then fired 5 rounds (each single loaded in a mag) of the factory WW Super-X 93gr FMJ. Again, not one round locked the toggle back and the velocity was still in the 1050fps range. Not only that, but some of the rounds either didn't extract and eject or stovepiped. I really think this new Wolff spring is quite a bit stronger than the original. I then did the same with the Fiocchi JSP. Those 5 rounds also failed to lock the toggle back and and two failed to extract/eject. The toggle was closed tightly back over the fired rounds. The velocity of the Fiocchi ammo was in the 1060 fps range.
So now I moved on to my reloads. My first try was AA#5 and a 90 grain XTP .308 (not the .309) bullet. I used 5.8 grains, 5.9 and 6.0. None of these loads locked the slide back and average velocities ran 1048, 1062 and 1078 respectively. A few of these either remained in the chamber or stovepiped. Next I tried a slower powder, AA#7 with the same bullet at 7.1, 7.2 and 7.3 grains. Success! These rounds extracted perfectly when fired and every one locked the slide back. 7.1 grains gave 1119 fps, 7.2 = 1131 and 7.3 = 1145 fps. So it does seem like 1100 fps is the magic number for my Luger. It doesn't look like AA#5 will do for me as 6.0 grains is up at recommended max and still over 20 fps slow for the magic 1100fps.
There were no signs of pressure buildup on any of these loads.
Next I am going to try Unique, as I see many recommendations for this powder.
The main thing is I now know my Luger can function correctly once I get rounds reasonably over 1100fps. Now to work up a good consistent reliable load above 1100fps without any pressure signs. It was a good feeling to have the pistol functioning in the semi-auto mode, just like it should!
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