ballman6711
Member
I wouldn't trust that calculator, those pressures in psi are way too low to be correct.
chris
Universal Clays & .45 ACP
- Thread starter jski
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I wouldn't trust that calculator, those pressures in psi are way too low to be correct.
chris
AJC1
Member
Exactly my thought....
There's a very lengthy thread on this very forum/website discussing converting cup to psi: Converting CUP to PSI
In there they give a SAAMI formula used for that pupose: PSI = -17,902 + 1.51 * CUP
Which is used by the calculator:
So, unless there's a problem with that ...
ballman6711
Member
https://www.shootingsoftware.com/ftp/psicuparticle2.pdf
The thread you've linked to has this article in it. I would advise reading it.
From the article:
About 2/3 of the time, the
formula will land you within 3,000 PSI, so exercise appropriate caution. Also, do not
attempt to use this conversion for handguns or shotguns, or to use it outside the range
shown.
chris
The thread you've linked to has this article in it. I would advise reading it.
From the article:
About 2/3 of the time, the
formula will land you within 3,000 PSI, so exercise appropriate caution. Also, do not
attempt to use this conversion for handguns or shotguns, or to use it outside the range
shown.
chris
ballman6711
Member
I don't believe there is any direct correlation between CUP and PSI. You MAY be able to estimate it, but that's up to you.
The 16,800 CUP reading does look low, but they may have found that the pressure spikes when going up a tenth or two with that powder, and so stopped the data at that level in order to keep it safe.
chris
AJC1
Member
They are not directly convertible. It's not like converting temperature. The devices used and the accuracy of the devices is vastly different. Cup data is barely good enough to prevent rapid disassbly. Using extraction as a Guage is just as good as cup.
Take great care if/when one uses any conversion between CUP/PSI. In fact it is not a conversion.
Rather, it is a least squares fit correlation (not conversion) to a scatter data plot, and can be way off for any particular cartridge.
See https://www.shootingsoftware.com/ftp/psicuparticle2.pdf
for better understanding and where the regression fit came from. (Denton Bramwell)
Note also that the European CIP correlation is much more precise than the US SAAMI conversion.
Note also (also) that no pistol data went into this correlation.
And in the case of the 45ACP, the Calculation result is considerably different from SAAMI actual.
Rather, it is a least squares fit correlation (not conversion) to a scatter data plot, and can be way off for any particular cartridge.
See https://www.shootingsoftware.com/ftp/psicuparticle2.pdf
for better understanding and where the regression fit came from. (Denton Bramwell)
Note also that the European CIP correlation is much more precise than the US SAAMI conversion.
Note also (also) that no pistol data went into this correlation.
And in the case of the 45ACP, the Calculation result is considerably different from SAAMI actual.
Last edited:
GeoDudeFlorida
Member
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- Dec 1, 2020
- Messages
- 11,118
Yup. There’s no direct conversion between CUP and PSI because they’re measuring two completely different mechanical processes: thrust force versus elastic stress. But, it’s a numbers game just like dice or roulette. Some players gotta keep rolling until they crap out.
The 45 Super max is 28,000 psi (true psi) -- 1/3 higher than the standard 45 ACP.
While it is not a "high" pressure cartridge in today's Eargensplitten Loudenboomer parlance,
it is one for 45ACP/1911 family.
.
`Got the Berry's HP-Hybrids in this evening
Loaded three each for velocity check (only) before sunset
Used modified Universal Powder factors in Quickload *
- 4000 kJ/kg powder energy content (closer to GRT's model)
- Ratio of specific heats of 1.200
- Burn rate factor of 4.000
- Progressivity factor to 1.2752 (borrowed from GRT) discussions
- Resized Starline case volume 26.5 (using resized volume for cartridges < 30kpsi)
Berry's HP-Hybrid/230gr/0.610" length
2.10" OAL
Universal Powder/5.9gr/FedLrgPstl
Gov't 1911/5" (using 17# spring)
Quickload Estimated: 17,222psi/859fps/100% burn
Actual Muzzle Vel(fps): 851, 858, 855 (LABRADAR)
For info only.
NOT A PRESCRIPTION FOR RELOADING
DO NOT USE OTHER THAN FOR CALIBRATION/WORKUP
* Offline discussion going back and forth w/ another well-respected Forum member
(Denton Bramwell being consulted)
.
Loaded three each for velocity check (only) before sunset
Used modified Universal Powder factors in Quickload *
- 4000 kJ/kg powder energy content (closer to GRT's model)
- Ratio of specific heats of 1.200
- Burn rate factor of 4.000
- Progressivity factor to 1.2752 (borrowed from GRT) discussions
- Resized Starline case volume 26.5 (using resized volume for cartridges < 30kpsi)
Berry's HP-Hybrid/230gr/0.610" length
2.10" OAL
Universal Powder/5.9gr/FedLrgPstl
Gov't 1911/5" (using 17# spring)
Quickload Estimated: 17,222psi/859fps/100% burn
Actual Muzzle Vel(fps): 851, 858, 855 (LABRADAR)
For info only.
NOT A PRESCRIPTION FOR RELOADING
DO NOT USE OTHER THAN FOR CALIBRATION/WORKUP
* Offline discussion going back and forth w/ another well-respected Forum member
(Denton Bramwell being consulted)
.
Last edited:
ballman6711
Member
Hodgdon's data for 45acp has both CUP and PSI. PSI is newer data, but either can be used safely.
chris
ballman6711
Member
I should add that I looked at 185 and 230 grain bullets (45acp) but didn't look at 45 super.
chris
chris
All I'm seeing is CUP (on the Website for 45ACP/230gr/Universal)
Is there an option switch somewhere ?
ballman6711
Member
I was looking at all the powders, not just universal. I should have been more clear.
chris
The only powders that have a PSI measure are non-Hodgdon branded powders: Accurate, Ramshot, IMR, etc.
Last edited:
GeoDudeFlorida
Member
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- 11,118
“That’s no good for a city like this.” - Callahan
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