Recently I read the following comment which I found interesting.., I hope others can verify or challenge the accuracy of the authors opinion... Thanks in advance

"Smokeless powders all deliver the same amount of energy per grain of powder, under ideal burn circumstances".

Without the benefit of having QuickLoad or similar software, I am hoping to load sub sonic loads in a number of cartridges, while still achieving enough peak pressure to obturate fairly soft cast (BHN 12) projectiles.

I am aware that weight, sectional density, bullet fit are all factors. My concern is not so much getting a bullet stuck in the barrel as it is Secondary Explosion Effect.
Ringed chambers being expensive not to mention the other potential dangers with gallery type loads.

Further, I'm sure the folks that author the reloading manuals have a good reason for "Starting Loads" {% burn and rate of burn}
so for me finding the right powder (bulky)
that gives minimum velocity is the goal.

Then use 5744, if you really want min velocity, safely.
But yes, powder burn rates are controlled by the shape of the grain, and sometimes coatings. It seems to be more alchemy than science at times. And canister powders are blended to yield consistent, historic burn rates; in ammo production, they just adjust the charge weight. I used to manage tank ammo production and we had different weights of M30 Propellant depending on the lot, to give the same velocity and pressure.

DPCD,
Thanks for the information and suggestion.
Do you know if there is a formula for determining the energy as it relates to the ratio of powder weight to case volume / capacity.
Most of the cases I reload for are large capacity, 45-70, 38-55, 35-40 etc.

THX

Bob

quote:

Originally posted by dpcd:
Then use 5744, if you really want min velocity, safely.
But yes, powder burn rates are controlled by the shape of the grain, and sometimes coatings. It seems to be more alchemy than science at times. And canister powders are blended to yield consistent, historic burn rates; in ammo production, they just adjust the charge weight. I used to manage tank ammo production and we had different weights of M30 Propellant depending on the lot, to give the same velocity and pressure.

Given that pretty much all smokeless powders are nitrocellulose and nitroglycerin, the statement is factual for the most part- all powders have the same energy content per gram.

The burn rate is how fast that energy is released.

Given the bullet moves, the size of pressure vessel changes, so to speak, as it continues to burn, so practically speaking, a fast burning powder gets higher chamber pressure in a firearm than a slower one, per same amount of powder, but since it is not continuing to produce it as long, the force on the bullet doesn’t continue as it progresses down the barrel. If you have your Pmax last for a few more milliseconds, you get higher velocity. A slower powder with more powder accomplishes this. Thus magnum rounds- they wouldn’t work any better safely than standard ones if all we had was a single burn rate powder.

If you want a slower velocity safely, you need to get some tested data. Using a slower powder will give less velocity than a fast if you keep the total powder mass equal, by less pressure, but you can get unreliable ignition, variable amounts of powder burn, and it may not consistently get the bullet out of the barrel.

Creating your own load recipes is an inexact science, and you need to be able to test (although some are done indirectly, like wildcatters typically do) by just velocity and imprecise case appearance criteria (which has been shown to not be at all accurate).

Certain powders are known to behave in a stable manner with regards to some variables. 5744 is one that effectively gives good reduced loads in large cases, as DPCD alluded to above, but you do need to follow the rules with it- don’t compress it being a big one.

Cartridges you list is the reason 5744 was developed; so guys would not have to use fast burning pistol powders with associated problems.
Plenty of data for what you want to do.
5744 is position insensitive and needs no fillers.
Energy? that is calculated by your projectile and it's speed; you can't relate powder to that.
Yes, do not compress 5744; I had a guy ring the chamber on a High wall 40-70 on the first shot on a barrel that I just had installed. He did not follow the instructions.

quote:

"Smokeless powders all deliver the same amount of energy per grain of powder, under ideal burn circumstances".

I thought that was the case with the old IMR powders. The burn rate was controlled by coating and shape. Don't believe that is the case between brands, single/double base etc.

quote:

Originally posted by ramrod340:

quote:

"Smokeless powders all deliver the same amount of energy per grain of powder, under ideal burn circumstances".

I thought that was the case with the old IMR powders. The burn rate was controlled by coating and shape. Don't believe that is the case between brands, single/double base etc.

I think that's right. The whole point of adding NG is more energy.

I think going double base is more getting more density to the powder.

Mass vs. volume thing.

If I recall my old chemistry, nitrocellulose and nitroglycerin are dealing with carbon/nitrate bonds for energy, and thus about the same. But 1 g of nitroglycerin takes up a lot less volume than processed nitrocellulose.

Thanks CR et.al.
Great info / observations..

Why not just use published cast bullet loads as opposed to attempting to re-invent the wheel?

cause nobody wants to just burn 10grs. of 130 y.o. Unique.
they gotta be all fancy and use the latest greatest 60 dollar a pound stuff.

Wstrnhuntr;

To answer your question;
The original post posed a question which was intended to help educate me on the relationship of case capacity and powder charges and the projectile weight.

My goal is to develop gallery loads.
Not all published data includes this information.
With appreciation some of the responder's provided some great information. Thanks to all.

Bob

quote:

Originally posted by Wstrnhuntr:
Why not just use published cast bullet loads as opposed to attempting to re-invent the wheel?

Using the closed bomb method of testing all cartridge-type powders yield similar energies per mass (weight) of powder, that is, within a few percent of each other. Slower burning rifle powders tend to yield a tad less than faster burning pistol powders simply because more of their mass is composed of non-burning chemical retardants. Powders will vary a little depending on whether they are straight nitrocellulose or a combination of nitrocellulose and nitroglycerine.

But that is highly academic since a gun is not a closed bomb and powders behave much differently depending on the ratio of powder to pressure vessel capacity, bore size, and mass of the projectile.

Almost no quick-burning pistol powder as you would use in "gallery" loads has been demonstrated to exhibit "SEE". The problem with small charges of quick-burning powder in a fairly large case is that of being positioned consistently with the primer, which can make a measurable difference in how it behaves. Just turn the muzzle upward prior to each shot to largely negate that problem.

Very interesting thread; myself, I use Trailboss for subsonic loads and the aforementioned 5744 for reduced loads. But given the current drought of reloading components, I might have to make changes when I get low on powder.