Simo,
My experience agrees with yours. A couple of years ago when I was experimenting with 7.65 Luger loads, I found that the faster powders were not the best for reliable functoning of the action. I found that Unique, Blue Dot & HS7 were more reliable than Red Dot, HP-38, W231 & Green Dot. I know that you are unfamiliar with some of these powders, so I will list them by a "rating mumber" that they are listed under in the following Burn Rate Chart;
http://www.reloadbench.com/burn.html
The larger the number, the slower burn rate
Red Dot-------------10
Vihtavuori N320---17
HP 38----------------22
W231----------------26
Unique---------------35
Vihtavuori 3N37----51
HS7-------------------59
Blue Dot-------------60
In the US, Unique has been the standard powder for loading 9mm for years. I have found that Blue Dot works much better, and it has become my standard powder for 9mm & 7.65. Incidentally, I got higher velocities out of a 6 in bbl than out of a 4 in or an 8 in!