Need a powder charge caculator

[RainDodger]

Hey, guys. I want to build a simple calculator, but I don't know Excel well enough to do it.

Suppose I have a 150 grain bullet with a minimum powder charge of 5 grains and a maximum powder charge of 10 grains.

That data would produce a line on a graph (or a sequence of numbers on a table), that would give you all the powder charges in between that min and max, for that bullet.

I'm looking for a calculator that will extend that line (or sequence) so that I can estimate a powder load for a different weight bullet.

So, if a loading manual only gives me data for a 150 grain bullet, using known data for that bullet, I want to estimate a powder charge for a different weight bullet. We all have a need to do this sometimes.

Has anyone put together anything like that?

 

[rcmodel]

Powder doesn't work that way.

The burning curve / pressure progression is not linier in the same caliber.
Let alone different calibers.

The closest thing I know of is a couple of good reloading manuals.

Or Quickload software.

Or the old Powley computer slide rule thing.
http://www.shootingtimes.com/2011/01/04/ammunition_st_powleycomp_200901/

That data would produce a line on a graph (or a sequence of numbers on a table), that would give you all the powder charges in between that min and max, for that bullet.
5 grains and a maximum powder charge of 10

That would be 5.1, 5.2, 5.3, etc, etc. up to 10.0.

rc

 

[RainDodger]

I know it's not precisely linear, but I'm looking for something to give me an idea - if you use a middle of the road load (not min, not max) and you're not changing bullet weights drastically, it should be close. For instance if I have good data for a 130 grain bullet but no manuals list that powder for a 115 grain bullet, I'd like a quick idea of what the charge could be.

Thanks for the info.

 

[rsrocket1]

Get the demo for Quickload and read the manual.
You will be limited to a couple of fake powders and hypothetical guns, but you can vary the parameters just like in the real program. You can also do a batch calculation of powder weights and then copy the data to notepad, then to excel and you can plot it. You'll see that the pressure and muzzle velocities are not linear and cannot be simply related to each other.

Here is a quick and dirty data run and what the relationship looks like:



I would not rely on Quickload when it comes to below minimum charges or above maximum charges. I would also not rely on muzzle velocity predictions with very short barrels (like 2" snub nose guns). It does seem to be very close to estimated muzzle velocities when you are in the middle of the charge range which makes it excellent for predicting how well alternate powders might perform in your gun.

 

[DC_art]

Sometimes the results are amazingly linear in the range between the starting and max loads. Here's how to do it in Excel:

Have the data in a table.
Plot the data in a scatter chart with straight lines
Add a trend line.
Display the equation for the trend line.
Plug your data into a cell using the equation given in the chart.

I did this for 155 gr bullets using Powder Pistol. There were 6 loads specified in the Hornady manual. My calculated MV came within 4 fps of the data from the book. So this can be used for interpolating the data between the starting and max loads but it would not be safe for extrapolating beyond those values.

 

[Rule3]

Buy a Hornady manual. They are the only one of the big three that give you four velocity readings for 4 powder charges. Not just a high and low. You can interpolate from that

With the data online and as many manuals as you can buy, you can usually find the charge for any weight bullet. If a certain powder is not listed it's usually for a reason.

Other than Quick Load I do not believe it is possible to make your own calculator.

 

[RainDodger]

Thanks a lot, guys. That's good starting information. Since I'm staying pretty much in the center of the min/max, I don't mind extrapolating a bit, albeit carefully.

As it happens, I've collected a lot of manuals over the years, so I've got many Hornady manuals up to the current ones. As a total side note, it's quite fun to look at some of the VERY early manuals like a loose leaf Speer manual from the 1960s. A lot of loads were pretty hot back then.

Thanks again.

 

[moxie]

Sometimes hotter than you think!!

For example, the Speer #11 for a 140 JHP and 17.5 grs. 2400 is listed at 1343 fps, six inch Security Six.

Using the Hornady 140 JHP over 17.2 grs. 2400 I chrono an average of 1485 fps, my FOUR inch Security Six.

I know, different bullet manufacturer, but, >140 fps with .3 grs. less, giving up 2 inches in barrel length.

The point here is that extrapolation is good for getting you in the ball park. But you really can't tell what's happening with a given load in your gun without a chrono. "Feel" and "observation", etc., are not the same as chrono readings.

Proceeding "carefully" without a chrono is, well, you pick your own apt analogy.

 

[ranger335v]

"I'm looking for a calculator that will extend that line (or sequence) so that I can estimate a powder load for a different weight bullet."

You won't find it because it isn't possible. if it were otherwise there would be instructions in any number of loading manuals. As RC said, powder burn rate is NOT lineiar, it varies by actual pressure much more than any "calculator" can even estimate. And it gets deadly FASTER as pressures increase.