Rich,

The concerns you have are certainly valid, but I wonder if you've ever seen a warning in any reloading publication to refrain from using the data in a top break? I think I've seen reference to good sound guns or some such, but never about cheaply made foreign and/or domestic products.

I fielded a question one time, from Central America, on a top break that was going to be welded up, so it was a single shot. The gun was in bad enough shape that the only way it was going to function was as a single shot, but it was all he had access to for home defense. I tried to persuade him that a machete was more reliable and less dangerous, but ended up trying to guide him into the least dangerous route.

The Speer #8 short barrel loads specify what they should be used in and also implies the heavier loads are for "K" (medium) frame type guns. It even says regular use of the loads in small frames will loosen them up, but people tend to ignore warnings or they're too ignorant/uninformed to know the safe/prudent thing to do.

There just isn't any way to cover all of the ways to not do something, even though the attempt is made with all of the warnings attached to any and everything made now. Even with that practice, there are still people doing things that will get themselves hurt.

In 1970, there were few instances of people suing a manufacturer for the results of their own less than intelligent actions. There was a premise of people being responsible for their own actions that was the basis for most things written at the time.

The whole situation just reminds me of the signature line I've seen, "ignorance is curable, stupid is forever."

quote:

Originally posted by WR Moore:
Just to pass on a thought about the "sudden" appearance of CUP labels on pressures at a specific time.

Could this be the time frame at which it became apparent that CUP pressures were not, in fact, the same as PSI?

Actually, from the literatureI've read, people knew way back in the early part of the last centrury that crusher-based pressure measurements were not equivalent to true pressures. Phil Sharpe mentions in hise "Complete Guide to Handloading" a conversation he had with Doug Wesson about the matter when Wesson said that he had problems with the crusher method. They new that "PSI" represented the wrong set of dimensions for the crusher pressures, but still used it for lack of a better one.

It seems that the CUP/PSI descriptions split when true PSI measuring techniques became widespread enough. Whether that was when the true PSI method was included in the SAAMI standards is the question, in my mind.

quote:

Originally posted by Paul5388:
I think Caldwell would have known of the SAAMI specs, since DuPont had been using transducers since at least the 1964 data they published.

Paul,

I had a brainstorm this aftrnoon while mowing the lawn on the above issue.

I found my old DuPont manuals from 1975 and from 1980. As I noted in an earlier post these use the "CUP" nomenclature for pressure. If you recall, I had speculated that the 1964 use of "PSI" for the pressures may have just been used because CUP had not come into use that early.

The idea occurred to me that CUP and PSI pressures are not equal: in general, 10,000 CUP does not equal 10,000 PSI. Somewhere in the conversion, the two are equal, and they diverge on either side of that point. Now if we look at the actual pressures that DuPont measured and found cartridges where DuPont did not refire the data, the pressures would have to be numerically different in your loading guide than in mine since PSI does not equal CUP.

There are three cartridges where the data were the same: .45 Colt, .22 Remington CF mag, and finally the .44 mag. Those are listed in ascending pressure, by the way, and span from 13,000 to 33,000 to 40,000 PSI/CUP. The interesting thing is that the charge weights are the same, the velocites are the same, and the PRESSURES are numerically the same. The only difference between your data and mine are the dimensions used for pressure. I don't know exactly where the two pressure curves cross one another, but it cannot be at all three pressure levels. The fact that all three very different pressures made the transition from one convention to the other says something very important.

There are only two possible explanations that I can think of to account for the lack of numerical difference between the two sets of data. Either, the DuPont engineers messed up and did not recognize that CUP and PSI were not equal, OR the use of "PSI" in the earlier data guide was simply a hold over from the earlier convention as "CUP" had not come into widespread use in the early '60s.

Mack,

My 10/99, 2004 and 2005 IMR Handloader's Guides are in CUP also, but they highest pressure shown in the 10/99 issue is 36,000 cup for the .357. That's 10,000 cup less than spec, but supposedly close to the psi spec.

The 1964 DuPont guide says a .357 with a 158 gr LSWC can use 9.5 gr of SR 4756 at 1345 fps and 34,800 psi. In 1999, the same bullet only uses 7.7 gr of SR 4756 at 1110 fps and 35,800 cup. What you're suggesting is, the 9.5 gr load is really cup, but that certainly wouldn't explain less powder having more pressure and less velocity in 1999.

It certainly appears to me psi is psi and for some strange reason, DuPont switched to cup at a later date.