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Old January 24, 2001, 08:45 AM   #1
vince weng
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when and why to choose fast burning or slow burning powder? Please explain?
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Old January 24, 2001, 09:03 AM   #2
Peter M. Eick
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Simple answer "when one is more accurate then the other and it meets your velocity requirements" ie: experiment and try different loads and see which one works.

Detailed answer: I personally tend to lean toward slower powders that fill the case more because it adds a safety buffer to double charges, but with that said, I still like 231 and bullseye (both fast) in my 45acp because it is accurate. Mostly in the rest of my guns I am shooting aa9 and blue dot (v slow) in the 10mm's, Power Pistol in the 40's and 9mm (medium) and aa5 and unique (medium) in the 380's.
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Old January 24, 2001, 09:46 AM   #3
vince weng
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other than accuracy, do they make any difference if I use gas operated gun (semi-auto) or bolt gun. The fouling problem, which one is dirtier?
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Old January 24, 2001, 10:36 AM   #4
Southla1
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Vince if you are speaking of rifle loads the slow burning powders are best for heavy bullets in standard cases and almost all of the bullets in cases such as the 7MM Rem. Mag or the 264 Winchester Mag. The use of slow burning powders and very heavy bullets is fine in bolt guns, but should NOT be used in a gas operated auto rifle such as the M1 Garand. The new Hodgden Manual has a special section devoted to loading for the M1 Garand. The best advice is to follow the recommendations made in the reputable loading manuals. When it comes to a load for the Remington 742/7400 series autoloaders try to duplicate the factory loads as closely as possible.
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Old January 24, 2001, 11:26 AM   #5
Poodleshooter
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Fouling is a function of at least two issues.
1. How naturally dirty a particular brand of powder is,
2. Speed of your powder burn relative to crimp
If you notice lots of fouling streaked down the side of casings (particularly pistol cases), than you need to crimp a little more (being mindful of pressure considerations)for that particular bullet and powder matchup. That will help you powder burn more completely. I would say that in general faster powders may tend to be a little cleaner as there is usually a lighter load of fast powder.
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Old January 24, 2001, 09:32 PM   #6
Chris McDermott
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Vince

It sounds like you are looking for general principles here for powder selection. It really depends on the relationship between case volume, bullet weight and caliber (diameter of bore). The case volume is the amount of space the powder has to start burning in, the caliber determines how much this space will grow as the bullet starts to move, and the bullet weight (inertia) helps determine how fast the bullet will accelerate.

Cartridges with small case volumes and light bullets (say 32 ACP for an extreme case) have to use very fast burning powder to get pressures built to give the bullet extra speed (velocity depends on pressure). Slow burning powders just wouldn't finish burning til the bullet was out of the barrel. Conversely a big case volume with heavy bullets, say a 460 Weatherby, needs very slow burning powder to let the bullet start moving down the barrel before it all burns up and builds way to much pressure, blowing up the gun. (yes, a case full of a fast pistol powder like Bullseye in most any rifle caliber will chop your rifle in half - in any of the popular actions Mauser 98, Remmington 700, Winchester 70, Ruger MkII etc)

Selecting the proper burn rate for your application is best done by looking in a loading manual.

AA #9, 2400, H110/W296 are very slow pistol powders, but in a rifle case they are really only useable for very light cast bullet loads, and the 22 Hornet (small case, light bullet) as they are just too fast. Conversely I don't think anyone has ever tried using slow rifle powders like H1000 or RL25 in a pistol cartridge; and I wouldn't even try. If the bullet sticks in the barrel it can cause a very sudden pressure rise as the rest of the powder then burns before the bullet can start moving again, producing dangerously high pressures.

For auto-loading actions that are gas operated, using a powder that provides the correct pressure at the gas port to work the action is critical for proper operation. Even for blow-back and recoil operated actions getting too far away from the ammo the gun was designed for will cause the gun to jam or beat itself to death as the amount and speed of recoil changes.
Example : Model 1911's in 45ACP for Bullseye target shooting typically use light 10 lb recoil springs with the light Bullseye target ammo of a 185 grain bullet at 750 fps. Standard guns use 16 lb springs for typical off the shelf ammo of a 230 grain bullet at 850 fps. Target ammo in a standard gun won't work the action and it jams/fails to eject on every shot; standard ammo in a Bullseye gun will beat it to death in short order.
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