Vihtavuori N320
The "competition" powder.  Shooting steel plates or need to shoot fast and accurate?  This powder is very popular.  Small charge, small recoil, clean, accurate...
N320 fills almost half the case with small loads, because its a good size stick powder

Titegroup on left, IMR 4756 in middle, N320 on right.  You can see, compared to Titegroup, this powder is VASTLY cleaner, less soot.  Among cleaner burning powders. 

Another angle of N320 not filling the case that much.  This is much different than Titegroup because this is stick powder. A double charge of this is vastly easier to see, as it would fill the case considerably. 

Another extruded stick powder. 
If you make a mistake, and double charge/load, which would be very unsafe as it would be huge pressure, with N320 it would be vastly more noticable than say, Titegroup, because with this, it would fill a great deal of the case, even using 147 grain bullets. 
This powder still is not what we would recommend for the beginner or starting out reloader, but then again, we recommend "zero" fast burning powders because of the potential of more dangerous pressure if you make a mistake loading. 
N320 is the competition powder for good reason.  It shoots what they call "soft", and is top tier accurate.  Its also economical too (compared to other VV powders), even for an expensive powder since you are loading, generally, under 4 grains per load. 
This powder is one of the hardest to find in times of shortage, due to the vast number of competitive shooters seeking it. 
We think this powder is the best you can buy for competition perhaps, but overall, its not versatile through the entire range of 9MM applications.  Becuase of this, it doesn't get a very high rating, because its a niche product for really only 1 specific purpose: Competing.

So...what about N320 and what do some cases look like?
  • Xtreme Case 12.75 grn capacity
  • Fiocchi Primer
  • 4.8 Grains
  • 1.095 OAL
  • 124 Grain Precision Delta HP
  • 1174 FPS
  • Red rimmed case in back is low pressure load, same primer, for reference. This is a higher pressure load with N320.  There is no need to show other cases, N320 is not made to go high velocity rounds, although, the above proves it can do acceptable velocity for self defense loads
  • 4.5" Barrel shot out of

Some of these loads are over manufacturer recommended maximums, DO NOT COPY or try!  Loading is always at your own risk.
As we can see, some of these loads are top, best you can get, accuracy and that is why competition people use it, along with its other favorable properties. 
We included different cases, to show different velocities using the same powder charge, and same bullet & OAL.  The case capacity matters a good deal, as you can see.

Some of the loads we tried
Load at your own risk.  What we load doesn't mean it will be safe for you. Do not load above recommended manufacturer book maximums.

Many of these loads are typical of what you would see on many ranges for shooting plates, for example.  Note many would not be allowed in competition because some cops require 130 PF minimum.

N320 burns cleaner
Compared to other powders that provide similar load data and results, such as Titegroup, N320 burns much cleaner.  Way cleaner. 
N320 is top row
IMR 4756 is middle row
Hodgdon Titegroup is bottom.  Look at the soot on the base of the case for Titegroup, and the discolortion on case compared to N320.