Neophyte, It's a bit subtle. Above #1 is the word Fastest and below the 147th is the word Slowest. This chart includes most powders available in the US for pistol, shotgun and rifle. Oddly enough, shotgun and pistol use the same powders. Rifle powders are way slower than pistol or shotgun.
Fast burning powders generate higher chamber pressure than an equal amount of slow burning powder. Sometimes that is desirable. Example: a target load for a 38 Special using lead bullets requires considerable chamber pressure to get the bullet to obturate yet you want a slow velocity. A light charge of Bullseye (a very fast burner) will do a perfect job. In the case of a magnum cartridge, you want to generate high velocities without exceeding the max allowable chamber pressure. In this case, you want a large charge of very slow burning pistol powder such as H-110.
If you were to categorize, #1-20 would be considered fast burning for pistol or shotgun.
#21-50 would be considered medium burn rate for pistol or shotgun.
#51-70 are slow burning pistol or shotgun powders.
Things get goofy when you get into rifle powders. Technically the rifle powders (#63 - 147) are in order of how fast they burn when not contained. Bottle neck cases change all of that. In one cartridge a given powder might rate "medium" whereas that same powder in a different rifle case could burn fast. With pistol powders, the burn rate might change a position or two on the chart, depending on the case used but in rifle, a change of 20 positions is not unusual.
The very best guide for powder burn rate is your reloading manual. When you look at the different powders for the exact cartridge and bullet weight, find a common velocity. The powder that takes the most grains to generate the common velocity will be the slowest burner and the powder that takes the fewest grains is the fastest burner. Powder density is not related to burn rate. You can have a very bulky powder that totally fills a case yet is a very fast burner. A perfect example of this is Trail Boss (not in the chart but is nearly identical to #5, Solo 1000). Typically, slow burners are more bulky (take more space in the case) than fast burners but this is not always true.
The concept for precision reloading is to find a powder that is the right burn rate for your cartridge case, bullet weight, and desired velocity. The right one will burn very clean, produce the lowest velocity spreads, and will be within the SAAMI chamber pressure limits, all while producing the desired velocity.
Most reloaders don't have the luxury of buying dozens of different powders so they tend to stretch the burn rate a bit. I know quite a few handloaders that use exclusively Unique powder for all pistol reloading. It is seldom the best powder burn rate for the intended load but it always goes bang and pushes a projectile down range. If you are happy with that level of performance, then who can fault you.
The more anal reloaders (my hand is raised) tend to experiment more in a quest for that perfect load. Over the years, I have managed to find excellent loads for all the cartridges and different bullet weights that I commonly load. I have about a dozen different powders at my reloading bench that cover about 20 different rifle and pistol cartridges.
I buy most of my powder at gunshows. Depending on type, it runs $16 to $20 per pound. So, 7 bucks /lb does sound good but .... the ad doesn't say it's AA#7, it says it's "crosses" with AA#7. That's not quite the same. Maybe it will load the same as real AA#7 ... maybe it won't. Personally, I'd rather buy name brand powder and know I can rely on the loading charts for accurate data.
As I stated in the above post, the right powder will burn very clean, produce the lowest velocity spreads, and will be within the SAAMI chamber pressure limits, all while producing the desired velocity.
To me, the least important attribute is burning clean ... the most important is tight max velocity spreads. I load a lot of Bullseye because it works really well in some of my match grade loads. Bullseye would appear to violate the rules because it's like burning dirt ... it leaves a lot of residue but not unburned kernels. If you see much unburned powder, it tells me the pressure is too low.
Keep posting, keep posting, gotta get to the library!!!!!!!!
Incidentally, used to load a lot of Bullseye and Unique (296 in .357). Recently read someone advocating 2400 in .357 Snubbies. Seems a faster powder would be better in a short barrel. Anybody wanna comment?
I buy my powder in 8 lbs caddies , Unique , 4227 and 3031 are the powders
I only stock .. I can find a magic load in one of these 3 powder . My rule of
Unique .............. up to 1000 fps
4227................. 1000 to 2000 fps
3031.................. over 2000 fps
If you own over 50 guns and used a special powder for each one , that
would be alot open cans of powder laying around getting old.. I shot alot
different types of comp shooting and made these 3 powders work for me
to bring the bacon home in the last 40 yrs.. And a deer can't tell you if he
was shot a bullet going 2800 or 3000 fps and if a drop of a inch at 200 yds
is not that important to me .. SO these 3 powders work for me