I was on Hodgdon's site and was looking at some loads and was wondering what is preferable when looking at different powder and bullet combos (on paper). I see some loads doing fairly close velocity wise (13fps) yet the pressure is 2300cup difference. On paper I assume you look for the powder that is going to give you the best velocity with the lowest pressure? I realize shooting actual bullets can vary from rifle to rifle.
Pressure vs Velocity
- Thread starter KDX
- Start date
In some cases yes.
Fast burning powders tend to create more pressure at a shorter length of time and vise versa with slow burning powders as a rule of thumb.
but like you mentioned "on paper"
also have a look at the amount of variance between pressure of the same powder on min and max charges.
compare that to another powder on the list.
Here is an example of some info comparison.
Looking at the hodgodn website for info on 45-70 trapdoor for 385 grain bullets.
H4198 min is 28 grains CUP 13300 max is 32 grains and CUP 14700 => 4 grains difference is 1400CUP
Compare that to the trail boss info for the same bullet.
Min 14 grain is 19400 CUP max is 16 grain and 23200 => 2 grains difference is 3800 CUP
If you compare the results you will see that trail boss builds more pressure with less powder compared to H4198.
I always keep this in mind when working up my loads.
Fast burning powders tend to create more pressure at a shorter length of time and vise versa with slow burning powders as a rule of thumb.
but like you mentioned "on paper"
also have a look at the amount of variance between pressure of the same powder on min and max charges.
compare that to another powder on the list.
Here is an example of some info comparison.
Looking at the hodgodn website for info on 45-70 trapdoor for 385 grain bullets.
H4198 min is 28 grains CUP 13300 max is 32 grains and CUP 14700 => 4 grains difference is 1400CUP
Compare that to the trail boss info for the same bullet.
Min 14 grain is 19400 CUP max is 16 grain and 23200 => 2 grains difference is 3800 CUP
If you compare the results you will see that trail boss builds more pressure with less powder compared to H4198.
I always keep this in mind when working up my loads.
You can also consider where/when the peak pressure occurs. In small capacity hangun cartridges say 9mm the peak is before the bullet travels 1/4" !! meaning the base of the bullet hasen't cleared the case mouth.
In most rifle cartridges, the peak is around an inch or so bullet travel, and in large, overbore cartridges, 2 to 3". From that point to the end of the barrel, the pressure is decreasing.
In most rifle cartridges, the peak is around an inch or so bullet travel, and in large, overbore cartridges, 2 to 3". From that point to the end of the barrel, the pressure is decreasing.
?
Far be it from moi to argue with a man of your experience, but it strikes me that burn time for a charge is not necessarily dependent on how charge volume. Chemical composition, granule shape, coatings, etc would be much more important, would they not?
ATOM; Charge volume is usually related to burn rate.
Slower powders require more volume to achieve velocity, thus filling the case more. Slower powders release their energy over a slightly longer period of time, thus the statement made by H4831 is usually valid.
Eagleye.
Slower powders require more volume to achieve velocity, thus filling the case more. Slower powders release their energy over a slightly longer period of time, thus the statement made by H4831 is usually valid.
Eagleye.
The correlation between load % vs pressure vs bullet weight and on, and on, was mostly developed by Homer Powley, to suit IMR powders.
His "Computer" will give you a rough idea of the best (IMR) powder to use based on multiple variables, then providing you with a relative quickness number wich can be used to extrapolate other's matching powder with the correct burning rate.
Say you have a relative quickness of 113, then, based on his computer, you will know you can deal with either IMR 4895 and / or IMR 4064. From his chart, the smaller the number the slower the powder must be. Also, usually, based on the former example above, if you take a powder having a lower relative numuber, for the purpose, let's say, 102, then, there are chances, even with a full case of this powder, you won't be able to reach the pressure / velocity you desire.
What you want to do is to fill the case with powder between 85 to 100 % of the case capacity for maximum efficiency.
Try the Powley computer here; h ttp://kwk.us/powley.html fill the first column and check the results.
If you need more infos about the Powley Computer, then read this; h ttp://kwk.us/powley_notes.html
His "Computer" will give you a rough idea of the best (IMR) powder to use based on multiple variables, then providing you with a relative quickness number wich can be used to extrapolate other's matching powder with the correct burning rate.
Say you have a relative quickness of 113, then, based on his computer, you will know you can deal with either IMR 4895 and / or IMR 4064. From his chart, the smaller the number the slower the powder must be. Also, usually, based on the former example above, if you take a powder having a lower relative numuber, for the purpose, let's say, 102, then, there are chances, even with a full case of this powder, you won't be able to reach the pressure / velocity you desire.
What you want to do is to fill the case with powder between 85 to 100 % of the case capacity for maximum efficiency.
Try the Powley computer here; h ttp://kwk.us/powley.html fill the first column and check the results.
If you need more infos about the Powley Computer, then read this; h ttp://kwk.us/powley_notes.html
If you like to experiment a bit, like reloading software vs paper, and/or frequently have questions like this, you may find "QuickLoad" software worth the price.
This is good software and lets you #### around with endless combination's of COL, powders, bullets,,, whatever,, and see how it translates into pressure changes, and distributions.
"QuickLoad" is one of those "not entirely necessary" indulgences that soon spoils you into making rather frequent use of it.
This is good software and lets you #### around with endless combination's of COL, powders, bullets,,, whatever,, and see how it translates into pressure changes, and distributions.
"QuickLoad" is one of those "not entirely necessary" indulgences that soon spoils you into making rather frequent use of it.
Maybe this is saying the same thing as already said, but in a different way, but every powder, possesses practically the same amount of energy per grain, it is just released differently. "Slower" powders reach a lower peak pressure, but maintain a higher average pressure than "faster" powders. If you limit peak pressures to say 50K psi, you will be able to use more of the slower powder than the faster, and hence will be able to safely pack more energy into the cartridge, and so your bullet velocity will be higher. All this assumes that you are operating the powder within its effective pressure range - faster powders can operate at as low as 10K psi, but many slower powders will not burn (or burn consistently) below 30K psi.
I usually choose the powder that's most accurate, and it's usually the one that operates at near max pressure while filling the case to 90%+ capacity - for rifles anyways.
I usually choose the powder that's most accurate, and it's usually the one that operates at near max pressure while filling the case to 90%+ capacity - for rifles anyways.
Quickload and Load-From-A-Disk both use the primary principle of the Powley Computer.
I use all of them. But the Powley Computer is free and you don't have to get a pirated copy to use it without paying.
I should have mentioned that the use of any program should be backed by a reliable source of loading datas.
I use all of them. But the Powley Computer is free and you don't have to get a pirated copy to use it without paying.
I should have mentioned that the use of any program should be backed by a reliable source of loading datas.
