"CUP, psi and Reloading Data"

Pumpkinslinger · Posted: Sat Mar 21, 2009 5:39 am Post subject: "CUP, psi and Reloading Data"

For those of you who haven't seen it already there is a very good article in the May '09 issue of "Shooting Times" on pressure measurements for firearms. "CUP, psi and Reloading Data" by Allan Jones. He confirms that there is no direct conversion from CUP to psi. By the way, Jones was the editor for the Speer reloading manuals for 20 years.

Bushmaster · Posted: Sat Mar 21, 2009 7:23 am Post subject: Re: "CUP, psi and Reloading Data"

Here we go again...Which is best. I remember the QS, SQ, CD 4 wars of the '70's. We all lost that one.

All I have ever used for reloading was CUP. I understand CUP. Now they want us to believe that PSI is better. Is that something like Metric is better then SAE? I wonder.

Pumpkinslinger · Posted: Sat Mar 21, 2009 8:48 am Post subject: Re: "CUP, psi and Reloading Data"

I don't think anyone said that psi is "better" necessarily. However, the equipment used to measure it is much more accurate than a copper crusher and can show you the entire pressure curve, not just the peak.

chambered221 · Posted: Sat Mar 21, 2009 9:47 am Post subject: Re: "CUP, psi and Reloading Data"

Working with any new system requires acceptance for change!!!

The hard part about it as in the SAE system is, those of us that grew up using it can look at a bolt or nut and identify it as the size it is. ½, ¾ or what ever it is. But even when we know it’s metric we will still look at it as SAE in our minds, then try and convert it to the metric system. If we would force ourselves to associate with the proper system from the beginning the change would become a lot easier.

As far as using psi or cup, I really don’t care !!!
All that matters to me is having a standard to go by and knowing its limits !!!

Bushmaster

Chambered...I took my apprenticship from 1958 to 1961 and was a journyman from 1961 on. I learnd in a Europian automotive shop and had to know SAE, Metric and an old English wrench that I can't remember how to spell. We do not need metric in the world I live in...Maybe the doctors and scientists need the meteric system, but not machinist and mechanics.

I understand the difference between CUP and PSI. They just need to settle on one and not keep listing both. Then the next thing I'll need is a chart for calibre & PSI equivelence...

chambered221

Bushmaster wrote:

Then the next thing I'll need is a chart for calibre & PSI equivelence...

That’s my point, quit using conversion charts !!!

You already have a head start on the caliber thing, I think !!!
You do know what a 7.62 or a 5.56 is, right. How about a 6mm Remington or a 8mm Mauser ??? Confused

Bushmaster

They don't have a conversion chart for CUP to PSI because as stated above they are not comparable with each other.

English Mike · Posted: Sat Mar 21, 2009 7:39 pm Post subject: Re: "CUP, psi and Reloading Data"

NATO has finally gone over to PSI for it's SAA specifications too - much better IMO.

Vince · Posted: Sun Mar 22, 2009 5:51 am Post subject: Re: "CUP, psi and Reloading Data"

quote="Chambered"]Working with any new system requires acceptance for change!!!

The hard part about it as in the SAE system is, those of us that grew up using it can look at a bolt or nut and identify it as the size it is. ½, ¾ or what ever it is. But even when we know it’s metric we will still look at it as SAE in our minds, then try and convert it to the metric system. If we would force ourselves to associate with the proper system from the beginning the change would become a lot easier. [/quote]

It funny you should say this Chambered. We changed over to the decimal system for money, pounds/shillings/pence to dollars and cents, in Australia in 1966 and to the metric system for everything else a few years later. All my schooling was done on the old systems. I still convert things back to the old system so that I have a more accurate picture in my mind of a measurement.

160 kph is 100 mph regardless
25.4 mm is 1" and 304.8 mm is 12" or 1 foot regardless
914.4 mm is 1 yard regardless
1 metre (1000 mm) is 39.36" regardless
1 kilogram is 2.2 lb and 6.36 kg is 14 lb or 1 stone regardless

I can visualise the Imperial measurements, but I just cannot get the metric measurements in the same way without converting them back to the Imperial.

Bushy wrote:

Chambered...I took my apprenticship from 1958 to 1961 and was a journyman from 1961 on. I learnd in a Europian automotive shop and had to know SAE, Metric and an old English wrench that I can't remember how to spell. We do not need metric in the world I live in...Maybe the doctors and scientists need the meteric system, but not machinist and mechanics.

I understand the difference between CUP and PSI. They just need to settle on one and not keep listing both. Then the next thing I'll need is a chart for calibre & PSI equivelence...

You don't mean the Whitworth do you Bushy? Also, what is a Journeyman mate?

Cheers, Vince

Bushmaster · Posted: Sun Mar 22, 2009 6:40 am Post subject: Re: "CUP, psi and Reloading Data"

Yup...That's it. Whitworth. And I could look at a bolt or nut and tell you if it was SAE, Metric or Whitworth in those days just a bit ago.

You start out as an Apprentice then journyman. While a journyman you have several levels until you can make Master. A lot of schooling and "aquired" experience from Apprentice to Master. I retired as a Master Marine/industrial Diesel Mechanic. I worked on the big ones like Fairbanks Morse, Enterprise, Packard, Electromotive (GM), Detroit (GM), Grey Marine (GM) and several others. Not to mention the many types of equipment driven by these prime movers like reduction gear, generators and pumps.

fnuser · Posted: Mon Mar 23, 2009 3:39 pm Post subject: Re: "CUP, psi and Reloading Data"

Hey Bush if it makes you feel better, it is pounds per square inch not kilograms per square centimeter, so it's not really metric

Bushmaster · Posted: Mon Mar 23, 2009 6:32 pm Post subject: Re: "CUP, psi and Reloading Data"

I'm well aware what it is. I've been dealing with PSI (pressure per square inch) and PSIG (pressure per square inch gauge) all my life. Or sense I was 17. What I said was that I had worked with them all an I still prefer SAE...Kinda prejudice that way...

PaulS

I prefer the PSI measurements just because with the crusher method you could have high pressure for a short time that would measure the same as a longer lower pressure load.
with PSI the measurement over time shows why some loads caused problems only after years of use and other loads presumably at the same pressure and never had problems.

RePete · Posted: Tue Mar 24, 2009 6:47 am Post subject: Re: "CUP, psi and Reloading Data"

Bushmaster wrote:

Chambered...I took my apprenticship from 1958 to 1961 and was a journyman from 1961 on. I learnd in a Europian automotive shop and had to know SAE, Metric and an old English wrench that I can't remember how to spell. We do not need metric in the world I live in...Maybe the doctors and scientists need the meteric system, but not machinist and mechanics.

I understand the difference between CUP and PSI. They just need to settle on one and not keep listing both. Then the next thing I'll need is a chart for calibre & PSI equivelence...

The British one's that you can't remember are Whitworth and British Standard Fine (BSF).

I don't think that it makes a hill of beans which units that you compare as long as they are the same.

For CUP they used a pressure barrel with a hole in the chamber area that corresponded to the cylinder that the copper pellet went into. Upon firing, the case ruptured and the pressure collasped the copper pellet which they removed and measured, then check against a table of crushed values for the pressure. I think that this allowed some operator error. PSI is more direct and is non destructive. I know of 2 methods of measuring PSI. 1 uses a strain gauge to measure the deflection of the chamber - used on a rifle/handgun and 2, uses a piezo electric transducer to measure the pressure.

fnuser · Posted: Tue Mar 24, 2009 5:43 pm Post subject: Re: "CUP, psi and Reloading Data"

I figured you did, I was just poking at ya.