Pressure limits

[meatyrem]

I am wanting to know the upper limits of cup. Is it 55,000? What is safe and what is not safe.

[Kevin Thomas]

You still don't have a question here, until you factor in the brass and the gun itself. These go all the way from fairly weak (both actions and brass) all the way up to hell for stout.

What, specifically, are you looking for here?

[meatyrem]

Just as in psi. Manuals list the psi and cup. Most of the pressures I'm seeing for cup tend to be around the ball park of 49,000 to 51 or 52,000. I have seen 54,000 to 54,500. My question is, anything over 55,000 too excessive. And with manuals is the 49,000 to 52,000 cup well under limits, are the numbers in the manuals very conservative?

[Kevin Thomas]

No, they're not conservative, they're industry standard. You shouldn't be seeing too muchin the way of CUP these days, since the industry is switching over to PSI or BAR figures. There's problems in judging pressure with copper units, and the more modern PSi figures are much more accurate. There is, incidentally, no conversion for CUP to PSI. They don't have a linear relationship to one another, and shouldn't be confused.

As to the older CUP numbers (and PSI, too, for that matter), each cartridge will have its own standard. Which cartridge are you looking for?

[meatyrem]

Well let's say, 280 rem. Most of the range of cup tend to be in the 47,000 to 51,000 or maybe slightly higher. I have seen higher, and don't know why it is they won't push it somewhat higher than what they do. It seems as if they could be holding it back from it's full potential. I was wanting to know how much under max are these loads that top out at around 52,000 CUP?

[Kevin Thomas]

I show 58,740 PSI as being SAAMI max for the 280, and wouldn't be too inclined to stretch it beyond that limit. I'm away from the office right now (NRA Convention) and don't have access to my reference material to se what the CUP rating was. In any event, as I said earlier, you should avoid CUP data whenever possible. It's outdated and a far inferior method of pressure measurment than the Piezo transducers used in most modern labs.

I'll be back in the office on Monday and would be happy to look up the CUP figures for you then. Just wouldn't advise relying too much on them when there's better, newer data available for you.

[Stonewall2]

http://www.saami.org/specifications_...wnload/206.pdf