Powders and burn rate

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First, it's a blast to finally be reloading, a mere year after I took Duke's class. I got into it because I was chewing through 40s&w ammo (sorry EC) doing action pistol shoots, but I'm sure I'll branch out from there.

Ok, so tell me about powder burn rates and how they impact the behavior of a load. I realize 40 doesn't have much of a range to play with when it comes to loads, but as I get into reloading other calibers, I'm really interested in the science. Here's something from another forum. Anyone have more to add?

http://thefiringline.com/forums/showthread.php?t=440419
 
In general terms, fast powders reach maximum pressure quicker, and stop burning quicker. Slower powders take longer to reach maximum pressure, and burn longer. As a general rule, the bigger the cartridge, the slower the powder. Rifle powders are slower than pistol powders.

Slow powders 'push' on the bullet longer and build pressure gradually, so they can provide maximum velocity loads with bigger bullets. You need more powder to do this, so case capacity can become an issue.

Also, load density can have an affect on powder burn rate and accuracy. Because most powders are position sensitive, having the powder only fill a small portion of the case can result in the velocity changing depending on where the powder happens to be positioned within the case when the round is fired. Try loading S&W .500 with AA#2 and you'll see what I mean. Actually, don't.

Every caliber has a maximum pressure and a practical range of bullet weights. The data in the load manuals takes this into account, and specifies powders with burn rates that will work within these parameters, and (where possible) mostly fill the case.

That's why you don't see .32 ACP loads with H110, and .50 BMG loads with Bullseye.
 
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Thanks EC. That makes sense.

Ok, so take .500 s&w as an example. When you're working up loads, do you settle into a couple of different powders based on 1) filling the case reasonably well and 2) the amount of pressure/velocity desired for a particular weight bullet? Or do you end up with a favorite powder for that cartridge and you just vary the weight depending on the desired pressure/velocity? What about other cartridges you like to reload?

There are many powder choices for each caliber, and I wondering what motivates the choice. For me, I picked Titegroup because it's what I picked during the class, and my loads turned out great at the range. So what are some good reasons to try other powders?

I guess there's a lot of experimentation involved in this hobby. I like that, actually. I suspect the amount of experimentation one can do depends heavily on the range of safe pressures available for a particular caliber. 40s&w doesn't have much of a range, which is fine for my purpose. That's more for mass production and lots of shooting fun. For experimentation on loads, I'll probably want to pick a different caliber.
 
The load data usually lists in bold what was the most accurate powder for said cartride. Don't think you are going to re-invent the wheel and try different powders, leave it to the scientists that work for the manufacturers and use test equipment we can only dream of owning.
 
These might help.

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For games like USPSA, you want a fast powder with a heavy bullet. This gives the shortest recoil impulse, but may feel snappy. A slow powder will draw out the recoil impulse over a longer time, taking longer for the sights resettle.

With compensated guns, you want something that produces a lot of gas to work the comp, which is slower powders.

Every powder will feel a little different. But with the endless possibilities of powder, bullets, springs. Just find one that meters well, shoots well, then shoot the hell out of it
 
Doug,
Some reloading books even include load details that might assist with choosing a particular powder. For example, the current Speer book has a notation in the .40 S&W section for a load which approximates law enforcement loads. That might be worth knowing about when you are loading to that kind of level and for self defense.

I saw a reference (when I started loading for .500 S&W Magnum) for a easy on the hands load for big bullets. After some digging, I find that the powder used by the commercial loading company was Trailboss powder. Dig a little more and I easily discovered the who's, why's, and wherefores for the use of TrailBoss in any caliber. It's sweet on the hands.

Another reason to choose one powder over another, having to do with speed of the powder is the commonality of the use of that powder among calibers you will reload for. While TrailBoss is the exception to the "there is no one single powder for everything" argument, typically, you might have several powders to deal with, to cover the calibers. And, it's often nice to have some that are common to several calibers.

Now, as others have suggested, you don't want to use a powder that doesn't make sense. The publishers of the current reload data books have done that homework for you. It's why I always tell student to stick to published (and proven/tested) load data. Going off the grid with regard to powder selection could be dangerous.

Use several reload data sources, and compare them for your caliber, and see what makes sense for you. If you're plinking, do what makes sense. If you're competing, see what other successful competitors are doing. There's usually a reason why they win.
 
I found a bunch of stuff out on the web about ballistics. I found one link on either snipershide or gunloads.com. it was very scientific and not exactly ru. Reading. If your deep into interior ballistics its all outthere.
I don't experiment I just try different load combo's with in the manufactures published data.
I found that the science of ballistics is another hobby with in itself. Digging to deep into it took more time away from reloading and shooting.
 
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