What is dif betwen CUP and PSI? I have not found someone that can tell me, Thanks

Copper Units Of Pressure. They use a special pressure barrel and insert a specific cupper crush unit and go from there. The use has been reduced with the use of computerised "stretch" of pressure sensitve units. Someone correct me if I'm wrong.

Gidday Kenny. I have often wondered the same thing. I sorta understood the crushing of the copper pellets and the measuring of PSI....but I didn't know how they related to one another....soooo, I thought damn it...Mr Google knows everything, I'll ask him. Below is a link to many of his answers. You will find the answer to your question in there.

I would answer it for you (now that I know ), but I think that it will make more sense if you read it for yourself from a number of different sources like I did.

Google Search on CUP vs PSI

Cheers, Vince

Sagebrushsniper, you're right. "Copper Units of Pressure" is determined by crushing copper slugs. PSI (Pounds per Square Inch) is an actual measure of the pressure, done by using strain gauges. There is no straight conversion factor between the two.

Keep in mind that you cannot translate between the two. C.U.P. is an absolute measurement based on a batch of identical copper pellets and no two batches are alike. Therefore, 50,000 c.u.p. does not equal 50,000 psi. Heck, 50,000 cup from one batch of pellets doesn't even equal 50,000 cup from another batch of pellets.

Thanks all.

Very interesting thread, I always knew that CUP and PSI were not the same. Whats interesting is the amount of difference between the two, and indiscriminate interchanging of either could land you in dangerous territory. As it has been said the CUP measurement between two "identical" cartridges can differ, but it was the only way of figuring out chamber pressures before the advent of electronics. Personally I think maybe the CUP system of measurement should be abandoned and PSI used exclusively, if only to eliminate the "confusion factor". Would I be wrong to say that the CUP system is essentially obsolete now that there are far more accurate methods and insturmentation?

M. G.

MGKelly wrote:

Would I be wrong to say that the CUP system is essentially obsolete now that there are far more accurate methods and insturmentation?

I think you may well be right MG. However, there will always be those that are more comfortable with the old unit of measurement....like me with Imperial/Metric measurements.

I learnt Imperial then had to change over to Metric, although I still convert cm and metres to inches and feet an kilometres into miles because they mean something to me.

Cheers, Vince

Vince wrote:

MGKelly wrote: Would I be wrong to say that the CUP system is essentially obsolete now that there are far more accurate methods and insturmentation? I think you may well be right MG. However, there will always be those that are more comfortable with the old unit of measurement....like me with Imperial/Metric measurements.

Now that piezo-electric strain gages have gotten dirt cheap, I don't see why CUP should stay around. CIP in Europe uses strain gages, but publishes in different units.

Just ask a subject of the given bullet if it hid to hard and if so back off a couple of grains! Ha never had a dog complain my 60 gr. .243 were going to slow, just were to accurate to dodge! Also brass last longer if not stretched at max pressure!

From what I'm reading in the loading manuals PSI is replacing CUP as time permits and for any new loads.

Pumpkinslinger wrote:

From what I'm reading in the loading manuals PSI is replacing CUP as time permits and for any new loads.

Thank god CUP isn't replaced by, get a hold of this mouthfull of metrication pap: 'kilopascals'.

Well, when you boil it all down its just a number for comparison purposes. I don't think many of us have a way to measure peak pressure (sure wish I did!) and there is no way to calculate it.

Pumpkinslinger wrote:

Well, when you boil it all down its just a number for comparison purposes. I don't think many of us have a way to measure peak pressure (sure wish I did!) and there is no way to calculate it.

Oehler says different:
Oehler Personal Ballistic Laboratory
Not cheap, but good things never are.

kenny wrote:

What is dif betwen CUP and PSI? I have not found someone that can tell me, Thanks

Try this see if it helps www.shootingsoftware.c...ticle2.pdf