One thing that I've found is the N line of powders can get quirky in temperature spreads. Tuning the week before you shoot or on the day of can result in better groups. This is why N133-135 is so successful for "group" shooters who load at the range. A simple adjustment in powder charge for atmospheric conditions of the day can impact group sizes.If I have one criticism of the VV N100 line of powders, it's that they seem to work at their best on a narrow spread of bullet weights. Maybe that's a single base characteristic?
I've tried N140 with 69 and 77 grain bullets in the 223, but it's a bit slow burning for that weight IMO. It's better with the 77 than the 69, at least.
I remember thinking at the time that I should try some N135 with the 69's to see what it would do.
I have what may be a shaky theory that the 223 works better with a powder that's slightly fast burning for the application than it does with one that's slightly slow.
I'm leaning toward trying the 55's with N133 and seeing what happens. It's interesting to see that the first line of VV's blurb on N133 is that it was designed for the 5.56 cartridge.