Two questions on powder

[BodyPiercingByColt]

I've searched the pages of previous posts, but can't find the answer to my question: I hope that doesn't mean that I've missed out on rampant common knowledge.
While I have reloaded .45 ACP before (with my grandfather, at HIS reloading bench which was already set up), l have next to zero true knowledge about it.

According to the website jeffersonian.therealgunguys.com: "There are lots of powders to choose from, and each has different properties. Using a rifle powder in a handgun cartridge might cause stuck bullets; using a handgun powder in a rifle cartridge will probably cause severe injury. Read those load manuals! Pick a load that gives the kind of performance you want and buy your components to match that load."
According to reloadbench.com's Burn Rate Comparison Chart, Nitro 100 has the fifth fastest rate of burn. However, MidwayUSA states that N100 is not meant for handgun loads and is only recommended for shotgun purposes.

Here's question 1: Why, if rate of burn affects velocity, efficiency, cleanliness, and accuracy (from my understanding), would you not want a faster burn rate in all cartridges? Besides a better deal when it comes to buying a single type of powder in bulk, it would seem to help also in terms of ease and safety (in not mixing up powders).
I'm supposed to start with minimum loads anyway; if "using a handgun powder in a rifle cartridge will probably cause severe injury" why can't I just use a smaller amount of handgun powder in a rifle cartridge? Aren't we looking for the same qualities in every cartridge?

Question 2: Since I do realize that I MUST go by a powder's intended use (but I am the type of person who likes to know why), what qualities should I be looking for in powder when I am reloading pistol ammo? Rifle? Shotgun?
What brands and "models"(/lines) are good for each?

Sorry for the long-winded post, and thank you in advance for answers.

[BSlacker]

Why, if rate of burn affects velocity, efficiency, cleanliness, and accuracy (from my understanding), would you not want a faster burn rate in all cartridges?

Burn rate is across the same application, rifle, pistol, and shotgun. Burn rate is only within a pressure range. Rifle pressures are much higher than shotgun/pistol pressures. Using the shotgun/handgun powder app the pressures are lower for shorter time. In rifle the pressure is two and three times as high for much longer. Then we will have different powders that are arranged in order of burn rate that is based on a burn rate test that isn't a rifle or shotgun or pistol. Thus they are ordered in burn rate on a chart. You won't always want the fastest burn rate. It might effect the harmonics of the rifle barrel different and you would want a different rate. Faster burn rates in pistol and shotgun will effect slide battering and wear and tear, wad performance and such.

what qualities should I be looking for in powder when I am reloading pistol ammo? Rifle? Shotgun?

Read several manuals. Chrono results and accuracy are a couple of things to monitor. How clean does it leave your guns. Don't forget cost. Does it meter well in your setup. Pistol ammo powder I like to use will spill over if double filled. Rifle has to measure well and not gum up the rifle.

[rsrocket1]

Here's question 1: Why, if rate of burn affects velocity, efficiency, cleanliness, and accuracy (from my understanding), would you not want a faster burn rate in all cartridges? Besides a better deal when it comes to buying a single type of powder in bulk, it would seem to help also in terms of ease and safety (in not mixing up powders).

Fast powders bring up chamber pressure quickly at the expense of being "exhausted" sooner. Many pistol/shotgun powders are double based meaning they have nitroglycerine mixed in with nitrocellulose. The different chemicals produce a different final volume of gas. You want a pistol powder to burn fairly quickly before the bullet goes out the barrel.

A rifle powder generates pressure more slowly as the bullet moves out of the case and down the barrel. More barrel time allows for more bullet speed and greater final velocity.

I'm supposed to start with minimum loads anyway; if "using a handgun powder in a rifle cartridge will probably cause severe injury" why can't I just use a smaller amount of handgun powder in a rifle cartridge? Aren't we looking for the same qualities in every cartridge?

Yes, you can use pistol powder in a rifle cartridge, but it would be for a very reduced load. It's often done for reduced recoil loads. The problem is that it is not a regular practice to officially publish or encourage these loads for liability sake with the powder companies.

I regularly use 10 grains of Unique under a 100 grain round nose bullet in my .308 for a low noise/low recoil fun round with my kids. This is compared to the standard 43 grains of H335 under a 150 grain bullet in full house loads.

You would never want to go that high with Unique because the maximum pressure would be about 4X the rated max chamber pressure of the gun and it would most likely blow up

Question 2: Since I do realize that I MUST go by a powder's intended use (but I am the type of person who likes to know why), what qualities should I be looking for in powder when I am reloading pistol ammo? Rifle? Shotgun?
What brands and "models"(/lines) are good for each?
Sorry for the long-winded post, and thank you in advance for answers.

A reloading manual would be real good here. In a nutshell, fast powders for pistols and shotguns, slower powders for rifles. Slower powders for larger cased cartridges and faster powders for either lighter loads or lighter bullets.

Most manufacturers will state what their particular powders are best suited for.

Take a look at Handload.com and surf their database not necessarily for exact load data but for what type of powders are use for the cartridges you are interested in. Once you've narrowed it down, you can usually find starting points for your particular case/bullet/powder on the manufacturer's website.

Good luck and welcome to reloading