Blue Dot is my favorite powder for use in the 9mm Para. In my guns it gives superb accuracy and reliability, the best of any powder that I have tried across the wide spectrum of 9mm's that I own and shoot. The only negative that I've found is that it can have a noticeable muzzle flash, but it doesn't bother me while shooting. Its' slower burning rate seems to give a recoil impulse that allows it to function extremely well, and absolutely no chance of a double charge...
The 8.9 grain load with 115 grain bullet is far too hot for use in a luger (I have used 8.8 grains with a 115 grain bullet in my Sigs and Glocks without a problem, but it really is a +P load with velocities about 1,300 fps.). Particular attention needs to be paid to the overall loaded length of the cartridge, as seating the bullet deeper will raise pressures.
My current shooting loads that have proven to work well in my lugers is 7.5 grains of Blue Dot with either a 115 grain or 124 grain bullet, with an overall cartrige length of 1.169 inches (some hollow point bullets have to be loaded slightly shorter to give an equivalent functioning length equal to 1.169). The 115 grain load produces approx. 1,150 fps, and the 124 grain load approx. 1,080 fps out of my Sig 226's. They function very reliably in my lugers and other 9mm pistols. In several of my lugers they will produce 5 shot groups at 25 yards that run right at 1 inch. In my Browning Hi-Power GP Comp they will shoot groups under 3/4" at 25 yards. I haven't found any other powder that would do as well in my guns.
I know that others may not get the same results with Blue Dot that I have found, but I do know it performs extremely well for me in my loading and I'm very happy with it....
My 2 cents...