Quantification of powder burning rates.

[mehavey]

...forced to fall back to burn rate charts, when
powder of xxxx brand was not available...

What are you using to determine 'safely'?

[Kosh75287]

I'm not sure what the threshold is (~10,000 psi, I think), but above and below this pressure, certain powders far differently. Sometimes, the seemingly wacky positions of burning rate for the same propellant on different burning rate charts may be a result of their being tested at two different pressures relative to this threshold. Learned that from an engineer at one or the other propellant manufacturers.

[uscra112]

Each powder has its' very own threshold. Black powder has none at all.

[mehavey]

These two powders are right next to each other on the chart for (starting) burn rate



See anything "different" ?

NOTE:
7.5gr of one of these will produce 21,000psi for a 230gr 45ACP
7.5gr of the other w/ the same bullet will exceed 357Mag's 37,000 limit

[GregLaROCHE]

That’s a great example that explains that you’re not always comparing apples to apples.

[greenjoytj]

post #24, are the screen shots from the “Quick Load” program?

I see value units for example “Ba f(z)” plus others that I’ve never see or heard of before.

And “Vivacities”? I’ll need tI look that one up. Sound like quantified measurement of a pornstars enthusiasm.

[mehavey]

Ba = starting burn rate, which how burn rates are listed.
Vivacity is how that burn rate changes with both pressure and burn completion. *

Z is the horizontal axis (fraction of propellant burned)
Ba f(z) is burn rate as a function of that burn completion - i.e., the change in burn rate as things burn

Modern powders have the change in burn rate very carefully designed to match requirements.

Both Universal and Power Pistol start w/ near same burn rate.
But Universal accelerates very quickly and dumps its 4350 kJ of energy density right up front.
Power pistol is almost constant burn rate for a somewhat longer portion of the burn, with almost
20% more energy density during that burn.



* think Jitterbug vs Carolina Shag (pun intended)

[Larry Gibson]

Most all charts, if one reads the fine print, are relative burn rate charts. They are not hard and fast and should be used only for comparison. Because two powders are next to each other on any chart does not mean that load data for a specific cartridge bullet combination applies to the other powder. Especially one should not compare or derive any meaningful assumptions if comparing that powder in different cartridges loaded to different pressure levels. Some interpolation can be done if one is very experienced and understands the differences between the powders which are not based solely on the position of burn rate. Best to use proven, as in actual pressure tested, data.

[Bigslug]

Going back into the misty deeps of time, when I were a wee lad learning to read my Dad's American Rifleman magazines in the 1950s, experts cautioned strongly against trying to interpolate between powders in a "burn rate chart".

Those who fail to study history are doomed to repeat it. Those who DO study history are doomed to stand by watching helplessly while everyone else repeats it.

If ALL you have is a burn rate chart, then sure, you can get into trouble. But if you have a burn rate chart plus a few manuals that list different powders, pressures, and load density figures for reasonably similar cartridges, AND you've done enough homework on your firearm of choice to know the design does not possess an applicable Achilles' heel, then a burn rate chart can be your best friend in instances where cartridge data is lacking or powder types or bullet weights are limited.

The thing about rocket science: you should go into it recognizing that there is always the possibility that your rocket will blow up on the launch pad. Doing GOOD rocket science requires deep contemplation of where the border between "ZOOM!" and "KA-BOOM!" might lie, then slowly creeping up to it cautiously, poking it gently with a long stick. One of the handy things about the handloading field is that we have the ability to do this through studying 136 years worth of other people's smokeless "rockets", and - sorry to crush any egos here - the odds that you're actually about to try something massively new and innovative are really pretty slim.

So while a universally-accepted burn rate standard numbering system might be interesting, you can live quite happily without one assuming that you're willing to cross-reference across multiple modern and historical data sources. Frankly I'd rather do that than what you propose anyway - which is effectively strapping myself into the capsule of a rocket after taking ONLY ONE source's word for it that it's going to fly.

[Land Owner]

Dooph! Wish you had not mentioned that...

The thing about rocket science: you should go into it recognizing that there is always the possibility that your rocket will blow up on the launch pad.

With the Nation's eyes in sharp focus, we have a rocket launch to the Moon from Kennedy Space Center tomorrow morning at 8:33 a.m., or thereabouts...hopefully.

[facetious]

And don't forget powders marketed under different names , like h-110 and 296. One comes after the other on the list so is one faster?

[414gates]

[B]

Velocity is measured in feet per second, powder charges and bullet weight in grains, case length in inches...but powder burning rates seems to be strictly comparative; e.g.; "This one's faster than that one but slower than this other one." This may be wishful thinking, but it seems the industry should have a more precise means of measurement. What have I missed?

A sensible option is for each manufacturer to provide a powder density and energy content per unit mass.

Vihtavuori does that, the rest not as far as I can tell.

[mehavey]

That data (see https://castboolits.gunloads.com/sho...=1#post5449609) comes from individual closed-bomb tests.
As that kind of test/data is a function of a zillion other factors than just starting Burn Rate, it would be
more confusing (and even more dangerous) to the normal user who doesn't run internal ballistics software.

H-110 and 296(same powder/different label). One comes after the other on the list so is one faster?

It depends on the Lot# used in the bomb test.

...sensible option is for each manufacturer to provide a powder density and energy content per unit mass.

That wouldn't help the average handloader.
Again, look at https://castboolits.gunloads.com/sho...=1#post5449609
PowerPistol has a considerably higher energy density than Universal
Yet produces lower pressures because the change in burn rate once ignition starts is considerably lower.