#### lepcur1748

##### Active Member

These are nice. Thank you!

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter Mike6158
- Start date

Help Support Long Range Hunting Forum

These are nice. Thank you!

Just did this to estimate ANSI PSI to ANSI CUP and back. Wanted to estimate/convert Hodgdon 6.5X47 Lapua CUP load data to PSI.

Reference:

View attachment 251985View attachment 251986View attachment 251987

SAAMI stated in their pressure standards documents...

I'm a firm believer in science and math but they need to be balanced against reality so that we don't go astray when our theories lead us down the wrong road. I agree that coming up with a conversion is handy but I don't trust the basic CUP to begin with so converting a less than perfect pressure unit to another pressure unit doesn't make the numbers any more real. I would feel comfortable working with CUP values as long as my loads were not on the hot end of the powder charge map. The closer you push your powder charges to the top end the less comfortable I'd be using anything short of actual instrumentation.

The correlation between CUP & PSI was based on the graph (regression) shown in:

Reference:

https://www.shootingsoftware.com/ftp/psicuparticle2.pdf

"An R2 value of .927 puts an end to all discussion about whether PSI and CUP are correlated. They are. To prove otherwise, you would have to prove that .927 is a lot closer to zero than it is to one, and you’d have to show that the data pattern in the graph is much more like a shotgun pattern than it is like a straight line. An F value in the low teens is usually enough to show statistical significance, and we have an F value of 357.4."

and

"About 2/3 of the time, the formula will land you within 3,000 PSI, so exercise appropriate caution"

This is an*estimate* - like plus /minus 3,000 psi - the dots on the graph describe a straight line but do not fall exactly on the straight line. Data or ANSI PSI/CUP data pairs for 30 cartridges were used to develop the graph - good data input using established stat methods.

Kind of looks like a real good relation to me (almost 1 on 1), not theoretical, but that 3K psi added might make for a blown primer or sticky bolt lift or worse. Creeping up to max using reasonable increments still looks good - again it's just an*estimate/convert..*

Reference:

https://www.shootingsoftware.com/ftp/psicuparticle2.pdf

"An R2 value of .927 puts an end to all discussion about whether PSI and CUP are correlated. They are. To prove otherwise, you would have to prove that .927 is a lot closer to zero than it is to one, and you’d have to show that the data pattern in the graph is much more like a shotgun pattern than it is like a straight line. An F value in the low teens is usually enough to show statistical significance, and we have an F value of 357.4."

and

"About 2/3 of the time, the formula will land you within 3,000 PSI, so exercise appropriate caution"

This is an

Kind of looks like a real good relation to me (almost 1 on 1), not theoretical, but that 3K psi added might make for a blown primer or sticky bolt lift or worse. Creeping up to max using reasonable increments still looks good - again it's just an

Last edited:

Thank you for sharing!I've built a couple of spreadsheets that I think are handy so I thought that I would share them with the reloading community here.

I use one for documenting my load when I use a chronograph. It calculates the following for a 1 to 10 shot group for 7 different loads:

Number of shots

Lowest velocity

Highest velocity

Average Velocity

ES

Energy in ft. lbs

SD (note- Standard Deviation is a statistical value. 10 data points is the least number recommended by most chronograph mfgs and a very small sample. Statisticians will tell you that SD is only as good as the number of samples and they generally wrinkle their nose at a sample as small as 10. If you have less than 10 data points the spreadsheet will still calculate a result but it's probably not of much value)

Just fill in the blanks that you can before you go to the range and add the velocity and atmospheric data once you get there and start shooting. I take a printed copy with me but it will load on to a PDA (I loaded it on my Dell Axim 50). Once you get home you can type in the recorded values and do file Save As and save a copy specific to a particular test.

I also use the sheet when I don't use a chronograph. It's handy for keeping track of what loads that I've tried. I also have columns to record atmospheric data as well as data about the load that I am testing (caliber, BC, powder, bullet, etc.). The spreadsheet is protected to prevent accidental over writing of a formula. If someone wants the password I will gladly give it out. For that matter, if Len wants to include it when he edits the post that's fine with me. Who knows, maybe someone will get froggy and change the calcs to handle a larger sample size

I use the other spreadsheet to give me an overview of what charges I will use for a specific cartridge. When I go to the loading bench all I take with me is one sheet of paper rather than the manual. Once the loads are built I put the printout into the cartridge box with notes on which row contains which load. This doesn't sound like it would be that handy but I list every powder that I have on hand and I have a tab for rifle and a tab for pistol. I know this is going to make some long time reloaders wince a little but we have a lot of new to reloading people out there (that's a good thing). By listing all of the rifle powders on one tab and all of the pistol powders on another the likelihood of accidentally loading a rifle powder in a pistol case or vice-versa should be diminished since the "recipe" is for a specific powder is right there. Another benefit is that I only have load info for the powders that I have on hand. I don't have to worry about weeding through all of the other data. I thought about breaking it into caliber specific tabs but decided it would be more useful to more people if I did it this way. To tweak it to your liking just remove the powders that you don't have and add the ones that you do.

If Len posts the sheets that I sent him then they will already have data points entered in a couple of columns. Just delete the blue and red colored info. BTW- I used red to indicate max or over max charges in.

Feedback is appreciated but not necessary.

Well done.

Just using published data. Looking at the .224 88 gr. ELDM.

SD = .251, BC=.274, FF=.91

ELDM BC's might be inflated. Numbers need to be rounded - next revision.

SD = sectional density, a valuable thing for ballistic stuff.

Spread sheets are a useful tool for hand-loaders & shooters - spread sheet use allows for the display of data and calculations to provide such without using programming languages such as FORTRAN, BASIC & others.

The top display is a work-up of multiple rifles/loads that I use frequently.

The bottom two displays show the math involved in a two step process to produce the final results. The the middle one being the final energy calculation and the bottom one being the velocity calculation.

The math is from - SAAMI TECHNICAL DATA SHEET 1.0402A

you are welcome

Last edited:

BC = SD/FF and FF = SD/BC

In 2009, Berger Bullets introduced G7 BC’s for boat tail bullets. For those who are unfamiliar with G7 BCs, it’s simply a Ballistic Coefficient referenced to the G7 standard projectile instead of the G1 standard projectile. The G7 standard is a better match for modern long range bullets, so the...

bergerbullets.com

The spread sheet shown above shows SD, BC & FF values. I see that the ELDM bullets that replaced the AMax bullets have improved BC values. What the Berger link is saying is that if the BC of a certain bullet is in part weight dependent, a bullet with the same BC but weighing less can be driven faster and be a better flight performer.

The spread sheet calculates SD & FF from established diameter, weight, & BC values. The new .224 75 gr. ELDM driven at 3250 from a quick twist .22-.250 and having a sub 1.0 FF makes for a first rate long range yote & rodent bullet considering ballistics, recoil, economy (bullet cost & light powder charges), and terminal performance - swats down all rodents real good and expands well on yotes but not for pelt collection.

SD is a real consideration in both flight & terminal performance.