Optimum Pressure Range for Powders

[DonMountain]

I have been reading an old book "Handloading Ammunition" dated 1926 by J. R. Mattern and he mentions in several chapters about the optimal pressure ranges for smokeless powders. Generally he talks about shotgun powders having optimal burning qualities around the 10,000 pound pressure level with a usable range from 6,000 pounds up to 12,000 pounds. And of course pistol powders having optimal pressures of 20,000 pounds with a range of usefulness from 15,000 to 25,000 pounds. And similar for rifle powders. Has anybody seen recently an actual listing of this type of information for available current production powders? We can only get hints of this type of pressure/optimization range of powders by comparing the weights of powder needed to get to a certain velocity in the reloading manuals, by looking down the listings under a particular bullet load/velocity/pressure.

[RED BEAR]

I am not aware of any. There is the saami for cartridges but i am not aware of any optimum pressure for powders. Something along those lines would definitely be interesting.

[35remington]

Is there reason to believe if a certain powder is suitable for 8-10,000 psi for shotshell that it would not also work well in metallic cartridges at the same pressure range?

Something worth pondering. Lots of people do this. Is that “optimum?” If the load works well who am I to say that is not correct?

[samari46]

Memory is kinda hazy but the Lee handbook gives some information regarding Brinell hardness ratings and a formula that you multiply it by to get pressures you need to have the bullet to obturate (expand) to fill the bore of a barrel. Maybe this is what your asking about?. Frank

[Rcmaveric]

Memory is kinda hazy but the Lee handbook gives some information regarding Brinell hardness ratings and a formula that you multiply it by to get pressures you need to have the bullet to obturate (expand) to fill the bore of a barrel. Maybe this is what your asking about?. Frank

Thats for the lead. He asking about the powder. I have heard of this before. No real actual chart. I understand what he is asking. Most powders are designed for certain optimum conditions or cartridge. We mix and match a lot as cast bullet shooters. Like using shot gun powders in rifle cases.

I think from what i have read. Its been a while in long lost threads. Optimum pressures was a thing for slower powders. Like BLC2 and 4064. I tried them in reduced loads and they performed dismally for me. It was i was researching about why we dont reduce slow powders. They start acting wonky and burning weird. Its the pressures and flame retardants that help slower powders burn slower. Pressures not high enough and they can burn very erratic. If i am not mistaken, pressure is what helps all powders burn uniformly. So if you are getring high velocitie spreads then increasing the charge will help smooth that out and help the powder burn more uniform. I have heard a heavy crimp helps acheive the same thing because then it takes a higher initial start pressure.

There is a book called Powder Burn Characteristics that i have been wanting to read. It was just too expensive for me to get it. Not sure if it has the information in it.

When it comes to powders i am more interested in the peak pressure and pressure curve. Because thats how I determine a powders usefullness. I use a lot of Quick Loads though before i play with uncharted powders. Its fun to compare powders. I have what i normally use that i know works. It is fun and easy to find simmilar powders and with Quickloads to quickly tune a load. Sometimes it does good, sometimes better and sometimes worst.

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[Bazoo]

I've been studying on this myself. Along with loading manuals I've got a copy of propellant profiles 5th edition that is useful. Understanding not only a powders burn rate, but it's optimum pressure range and loading density range is something that takes a lot of research. I think it's a subject avoided by most reloading manuals because it's not something the common reloader can understand or needs to understand to assemble safe ammo.

Some powders are more versatile than others; such as 3031, 2400, unique. These are generally powders that's found wide application and thus became popular in times past for their versatility across the board.

Some powders only work well in their given range such as WSF, h335, and 296. To use these powders outside their optimum pressure ranges or load densities is asking for disaster. Sadly these powders are ousting the older powders as they excel in their specific applications, and new loaders seem to be only interested in optimum performance.

Personally I'd rather have a powder that's a little more forgiving, but lose some of the performance. And of course there is a middle ground, 748 comes to mind.

[Rcmaveric]

Is there reason to believe if a certain powder is suitable for 8-10,000 psi for shotshell that it would not also work well in metallic cartridges at the same pressure range?

It will work well. It just wont act the same. Think of the vessel size and bore size that the gasses have to fill. So in each instance of case size and/or bore size that powder will act completely different.

I dont think fast powders are prone to pressure optimums. Most fast powders are completely consumed within the first inch or so of bullet travel.

Also cast bullets have much lower start pressures and slip through our barrels quicker than jacketed. So pressures can be harder to generate due to the rapid blead off. Thats why i personally think fast powders work better, but that is just speculation.

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[BNE]

This is an interesting topic.

I know that there are unburned pellets exiting the barrel when using a magnum powder. (Think 357 and H110).

I assume that explains the large flash visible on Mag loads.

[Rcmaveric]

Cast bullets start into the barrel when the primer goes off unlike jacketed bullets. So most often unburned powder is cause by the powder being blown down the barrel before it had a chance to fully ignite.

Muzzle flash is caused by the bullet exiting while the powder is still burning. Once the bullet exits, oxygen hits the flame and causes a quick flash burn. Inside the barrel the flame is self oxidizing and has limited oxygen.

I prefer to use Blue dot and SP primers in my .357 mag. I have shot stout loads with Mag primers and 2400 with different primers. Accuracy was better at lower velocities and pressure. Muzzle flash and unburned powder is wast of money due to wasted energy not being used. If it gets you too yiur goal then I can support that choice.

What always confused me is that mag primers make slower powders act like fast powders. So what is the point of using Mag primers then or slower powders. I think if slower powders didnt work with your normal primers then enstead of switching primers, switch your powder.

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[DonMountain]

I've been studying on this myself. Along with loading manuals I've got a copy of propellant profiles 5th edition that is useful. Understanding not only a powders burn rate, but it's optimum pressure range and loading density range is something that takes a lot of research. I think it's a subject avoided by most reloading manuals because it's not something the common reloader can understand or needs to understand to assemble safe ammo.

Some powders are more versatile than others; such as 3031, 2400, unique. These are generally powders that's found wide application and thus became popular in times past for their versatility across the board.

Some powders only work well in their given range such as WSF, h335, and 296. To use these powders outside their optimum pressure ranges or load densities is asking for disaster. Sadly these powders are ousting the older powders as they excel in their specific applications, and new loaders seem to be only interested in optimum performance.

Personally I'd rather have a powder that's a little more forgiving, but lose some of the performance. And of course there is a middle ground, 748 comes to mind.

This ^ is the information that I was asking about. We have probably all tried to use a left-over container of powder designed to operate within a 50 BMG shell that we bought cheap and loaded under a cast bullet with a primer load of Red Dot, and found that it just didn't work. So, I was looking for a reference that I could use to "rule out" certain powders for certain applications that wouldn't work very well or give me consistent pressures and velocities. And select a powder that would operate within its design pressure range.

[35remington]

If powder is unconsumed in the barrel when pressure and temperature are much higher, why would it suddenly ignite when leaving the barrel as temperature and pressure plummet toward zero?

It wouldn’t. Muzzle flash isn’t umburned powder leaving the barrel and then combusting. As mentioned previously, it is due to the gaseous byproducts reacting with atmospheric oxygen.

[Bazoo]

I found this but haven't read it yet. Phone won't work it so I'll have to wait to use the computer. https://pubs.acs.org/doi/abs/10.1021/ie50257a006#

[DonMountain]

I found this but haven't read it yet. Phone won't work it so I'll have to wait to use the computer. https://pubs.acs.org/doi/abs/10.1021/ie50257a006#

This paper is concerned with "burning temperature" in this first page instead of the question I have concerning the optimal pressure for use of different powders. Or stated in another way, the optimal design pressure for a given powder and the optimal range of pressures usable for a given powder in our use for lead projectiles.

[Bazoo]

Like I said, I didn't check it out.

[Larry Gibson]

Has anybody seen recently an actual listing of this type of information for available current production powders?

No and you probably won't other than generalizations as noted. There are just too many variables to set an absolute figure. Burning rate, type of powder, primer used, mass of bullet, expansion ratio, temperature of powder, time pressure curve, time under the pressure curve etc. ad nauseum........

Each powder has it's own psi level where it will begin to burn efficiently and continue to burn efficiently. We make many powders give some semblance of reasonable use outside their "pressure/optimization range", especially in cast bullet shooting. Using a duplex load with heavy for caliber cast bullets to get very slow burning powder to burn efficiently is one example.

[Bent Ramrod]

The old-time handloaders used to write about a given powder’s “balance point.” This was the pressure level beyond which the bullet velocity would only show a marginal increase as more powder was added, while the pressure would spike quickly and erratically. SR-80, and later, SR-4756, were supposed to be especially bad offenders in this respect.

This was, of course, way before the SEE phenomenon, where an undercharge could also raise pressures disastrously, began to be noticed and studied.

Handloading at the time was a much more seat-of-the-pants process; only manufacturers and a few test labs had pressure equipment, and a lot of experimentation was done by amateurs, using their guns in lieu of instrumented combustion bombs. They’d go up to the edge of possibility, and sometimes over it, and report the results, with the qualifier that this worked (or not) in their particular firearm. Infrequently, the amateur would send sample loads to H.P. White or Phil Sharpe to get actual pressure and velocity data.

You might be able to divine this “balance point” by looking through a modern loading manual that shows the pressure levels for minimum, optimum and maximum powder charges in whatever calibers they are using the powder in. It would be pretty approximate in the absence of the complete pressure/burn rate curve, and absent having your own pressure measuring equipment, I don’t see how such data, or, for that matter, the putative “balance point,” could be extrapolated to other calibers for which no data for that powder exists.

[John Boy]

I know that there are unburned pellets exiting the barrel when using a magnum powder.

For magnum powder use magnum primers. Example:
Accurate 300-MP, magnum pistol powder will not fully burn in 32-40 and 38-55 cases unless magnum primers are used

[biffj]

A book written in 1926 would have been in the infancy of smokeless powder development. At that time most of the worlds militaries were using flake powder made from extruded sheets of nitrocellulose and chemical retardants were very basic. Things changed a lot prior to and during WWII and more developments since then. Ball powders were invented and further developed, pressure curves changed and so did the science. I don't know of any more modern books describing these changes but there are papers and studies you can find if you search. In the 20's most rifle cartridges were working in the 40-50,000psi range and now we're seeing 60,000 plus regularly. Brass development has helped with that and so has the powder tech. I'd not put a lot of stock in the information of a book that age other than as historical data.

One other detail....some seem to think that most muzzle flash comes from unburnt powder but this is pretty much not the case. Most of the flash is due to the products of the burnt powder. Unburnt powder tends to leave streak or spark like flashes. The byproducts are what creates the huge ball of flame type flash. These byproducts are in high percentage hydrogen, carbon monoxide, and water vapor. The reason for the bigger flash from shorter barrels is that the higher pressure better mixes these gasses with atmospheric oxygen while there is enough heat to ignite the gas. You will still see streaks and sparks from unburnt powder but its the gas that makes the flash......

Frank

[savage308]

mp300 will burn completely in a 300 bo with a 10 inch barrel with a standard small rifle primer.