Where to obtain reliable pressure data?

[Naphtali]

Moderator:

I have no idea how to categorize this query. If it should be elsewhere, please put it where you think it should go.
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I run Macintosh OS 9.2.2. Under physical duress, I'll run OS X 10.3.9. I have searched for ballistics software compatible with my operating system that yields pressure data. I have identified nothing.

I have a USRAC/Winchester M1886 rifle that I want to have converted to 475 Turnbull, 50 Express (modernized 50-110), or 48-90 (.475-caliber on 45-90 brass). Handloading data having pressures acceptable to me -- between 32,000 and 40,000 CUP -- is not available.

1. What software can calculate reliable pressure data for these wildcat cartridges?

2. How close to reality are pressure data generated from the software?

What exactly does software require to do the calculation?

[Ricochet]

There is no Mac software comparable to Quickload. If you want to calculate pressures and such, you'll have to use one of those Windows system emulators and use Quickload. Or buy a cheap PC just to run Quickload.

[mike in co]

and its only a tool, its not "data", its reference info.
you would need to put a transducer on your rifle for real data.
i use quickload a lot, but lot to lot variations in powder, differences in primers, lots of brass often show significant differences in projected info and real world results.

sorry to hear about your affliction( mac user).


mike in co

[Dark Helmet]

Dunno how much it'll help with your straightwall cases, but here's the Powley computer online. http://kwk.us/powley_notes.html#standards

[MtGun44]

Calculated pressures are THEORETICAL and and be a great place to start
for unknown wildcats or unusual powders (of course unusual powders
are unlikely to be modeled in the software). Powley was a pioneer and
his slide rule has been useful to me for many years. Limited powder
selections, but still useful. I have not tried the newer stuff, too cheap.

This is not an accurate way to get ACTUAL pressures, just guidance and
for "average" chambers, bores, throats, cases, primers, etc, etc. Very
useful, but not highly accurate for a particular situation.

I have been doing computer modeling for the gov't for 30 yrs and am
very aware of the benefits and the limitations. Not knocking the software,
just making sure we understand that it is theory (good theory) but not
the same as experimental work. Of course, even with solid experimental
work (actual pressures) your gun is a thing unto itself. This is why even
with a SAAMI chamber, "normal" brass, cannister powder, etc. you back
off at least 10% to start. I have seen blown primers at the FIRST load
on the 'beginning load' charts, too.

Bill

[Harry O]

I have been using the Powley Computer for years, too. When I got my first chrono, I was surprised at how accurate the velocity was measured at compared with the Powley prediction. I have always assumed that the pressure part of it was also accurate.

BTW, the velocity is supposed to be within about 5% of true (this is from memory) and when I have tested it, it has always been less than that. The pressure is supposed to be within about 10% (again from memory). It is a good starting point, anyway while keeping a close eye for pressure signs.

You should do an internet search for "Powley Computer handloading". There are several places that have interactive Powley programs that you just fill in the blanks and the velocity/pressure pops out. I don't know if they work with your operating system, though. One think to remember that the Powley Computer takes a large number of ACCURATE measurements in order to work. Read what the variables are, accurately measure them, and plug them into the calculations. The more accurate you are, the more accurate the results.

[JIMinPHX]

To actually measure pressure, you have two choices. You can use a copper crusher, or a piezio transducer.

The copper crusher is the old method & gives you results in CUP (copper units of pressure). This method basically involves letting the chamber pressure crush a copper pellet, then measuring the deformation & calculating the CUP from the deformation dimensions.

The piezio transducer method, involves taking down a small section of your receiver with abrasives to mount the transducer. You then need “proof loads” that you buy to calibrate the output of your transducer. If you are looking to make your own wildcat, then proof loads are not going to be available. You will probably have the same problem with obsolete calibers. Once the transducer is calibrated, then measurement can commence. This method gives you results in PSI.

The copper crushers are on their way out. Almost nobody is using them anymore. You will see CUP listed in reloading manuals for older cartridges like .38 S&W, that have been around a while. You may also see PSI data for the old ones. The PSI data is probably newer. More recent calibers like WSSM series stuff will likely only have data in PSI from most sources. There is no accurate way to convert from CUP to PSI or visa versa. They two systems of measurement are not linear to each other.

[The Double D]

If you want to check pressures, http://www.shootingsoftware.com/index.htm