Questions about powder differences

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tube_ee

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After burning up our first pound of powder, Bullseye, my loadin' and shootin' bro and I decided to try some different powders. Due to getting a sweet deal on Bear Creek .358 158gr LRN bullets, (9 bucks for 500... all gone now... we bought around 12 boxes...) we won't be changing bullets for a while, so we're playing with different powders. We're trying Green Dot and Blue Dot. And this leads to my questions.

1. It seems like the best-shooting Green Dot load is a little lighter than the best Bullseye load with this bullet, even though Green Dot is only ~78% as fast. 4 grains was the best load with Bullseye, and 3.5 is sweet with Green Dot. Based only on burn rate, you'd think this would be the other way around.

2. While Alliant and many other sources list 38 special loads using Blue Dot, I got very poor burn. Lots of unburned powder. Blue dots still blue. It wasn't until I got up into the low-end 357 magnum range (9.6 and 10.3 grains) that it burned well. Is this more a function of the bigger charge, or the magnum primers? It's obviously some of each, but likely not 50/50.

Thanks, experienced loaders, for allowing me to pick your brains.

--Shannon
 
I don't think you can necessairly determine what the powder charge is going to be based on burn rate. As for unburned powder at lighter loads; that's easy. You have less pressure and heat with lighter loads and more with heavier loads. Increased heat and pressure ensures more prompt and complete burning.

A couple of things I've found out about powders and bullets. Finding the right powder in a particular cartridge with a particular bullet weight and can make a huge difference in accuracy that doesn't seem necessairly related to burn rate. Also, bullets are not created equal even though they look superficially very similar. If you have a gun that is accurate enough to tell, you will find that the bullets of some manufactures suit your gun much better than others. Bottom line, experiment more. Of course in a handgun, you're not as likely to notice small differences in accuracy so it doesn't matter as much.
 
The Blue Dot burning seems normal for a medium/slow powder. Powders have a pressue range that they will usually burn cleanly in, the slower the powder the higher the pressure needed to get that cleaner burn. Fast powders are usually burn cleaner at lower pressures.

Fast powders (like Bullsye/Red Dot/700X) are the best choices for lite-loaded target ammo...the powders burn well at lower prssure and the charge weights are small and economical. Are some differences in the density of the powders...some are "fluffy" (take up more volume for a given weight) and some are dense. Geberally, will try to use the "fluffy" powder in a case with larger volume and the dense ones in the tiny cases.

I haven't had your reaction to green Dot..but i use little of it. Use a good bit more Red Dot (it's one of the fluffy ones) but have always belived it burns a tiny bit faster than Bullseye.
 
Powders have a pressue range that they will usually burn cleanly in, the slower the powder the higher the pressure needed to get that cleaner burn. Fast powders are usually burn cleaner at lower pressures.
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Not sure this is correct. Actually, faster powders burn more rapidly and create a quicker pressure spike. Slower powders release their energy over a longer period of time.

With light loads of slow powders, the pressure never does build high enough to get a good burn. The coatings used to control (retard) the burn rate do their job too well, hence the unburned powder.

Pressure comes from heat. If you don't get hot enough, you don't get a good burn. You'll also gete erratic velocities. HTH
 
Have to admit, for the fraction of a seond that a powder burn lasts, there isn't too much distinction between heat and pressure. But the fast powders, proably by way of their lack of retardants, do burn best at low pressure n my experience.

Trying to get 2400 to burn at 15-18K (as in .38specials) is a task....but getting 700X, 231, or Red Dot to burn clean at the same presure isn't a big trick (and I'll admint, even dirty, 2400 gives more velocity at that pressure)

Holding things down to the same mid-range handgun pressure level, it's worked out that the fast powders are cleaner burning than the slow ones.
 
It's the heat that creates pressure...just like the pistons in a car engine. They move because the fuel burns and creates heat which expands and pushes the piston down (or the bullet out)

Fill a balloon with air and then put it over a lamp. The heat from the light will make the balloon expand.

Powders pretty much have the same energy in a given volume. It's the burn rate that determines how fast the energy is given off.

FWIW...the slower "dot" powders and Unique need to be pushed harder or they're dirty IMO
Holding things down to the same mid-range handgun pressure level, it's worked out that the fast powders are cleaner burning than the slow ones
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Exactly.
 
One solution is to mentally adjust: shoot black powder guns for a week or two, then all the smokeless loads seem to be clean.
 
I tried some standard pressure 2400 loads (from published manual) in .45 Colt with dismal results. Shot to shot variation big and lots of unburned and partially burned particles in the chambers and barrel.

Bumped the charge weight into the 'Ruger only' range and it burned great. Was testing in SRH .454 so it was OK to try heavy charges but it illuminated the need to match the powder burn rate to the pressure of combustion.

Blue Dot would be in the same boat. Magnum powders need to be run at Magnum pressures or they don't burn well. 38 Specials shouldn't need anything much slower than Unique for max performance. I'd stick to the fast end of the burn ratings for them.
 
Proably tried the same standard pressure 2400/45colt loads...with the same results.

Tride them in a 20" carbine with great results, but I don't think barrel length alone was the issue.

A revovler has a good distance for the bullet to jump to find rifling. That's also the same time that it would need INCREASED resistance from engravment to make the powder burn better. Rifle barrel has the rifling just ahead of the bullet, very little "jump" before a rise in resistance..which seems to get slow powders at standard handgun pressures burning a bit better.

Upping the charge to "Ruger" pressures gets it buring right too, but for different reasons.

So i went back and resiszed those cases in a .45acp die, expanded them with a .45acp expander, and loaded the same bulelts over the same powder charge. With the increased resistance of the very tight bullet/case fit, the powder burned noticably better (but still not "clean")...velocity increased...but I have to assume pressure also increased and it might have become a bit more than "standard pressure".
 
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