Author Topic: CUP = PSI cart?  (Read 2889 times)

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Offline EsoxLucius

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Re: CUP = PSI cart?
« Reply #30 on: April 09, 2008, 04:24:52 AM »
Bramwell was not comparing unrelated observations, like Super Bowls and Stock Markets, he was comparing two different ways of measuring what is essentially the same thing, firearms chamber pressure.

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As Graybeard pointed out there are cartridges where the cup is higher than the psi.  The simple fact that some cartridges have a higher cup than psi rating does not mean that cup and psi are not correlated.  These cartridges could just be an anomoly.  However, it does suggest that his numbers may be overstated because he did not include any of these cartridges.
10% of those used in the analysis have CUP higher than PSI.
Cartridge ANSI CUP ANSI PSI
35 rem 35000 33500
444 marlin 44000 42000
8mm mauser 37000 35000

If this gentleman wants to know what his rifle will withstand in PSI based on a chambering of a cartridge he only finds CUP pressures for he can be pretty sure that (CUP*1.51586)-17902≈PSI will get him close enough to make a judgment.  Using the chart that shows the CUP and PSI values for 30 or so cartridges, he can also compare the CUP value of his cartridge with the PSI values of cartridges with the same or similar CUP rating and evaluate it based on that.  Inference supported by data is a wonderful thing.

I would like to thank everyone for their patience with me on this matter.
We learn something new everyday whether we want to or not.

Online Graybeard

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Re: CUP = PSI cart?
« Reply #31 on: April 09, 2008, 10:58:53 AM »
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My question on pressure has always been, since SAAMI did not manufacture my weapon, and XXX Inc makes it in a 260Rem, a fairly high pressure round, why am I limited to say 3/4's of that pressure because mine happens to be chambered for 6.5x55 or say a 35Remington? What am I missing here? Seems like I don't need to buy another rifle, but to simply upgrade the performance of the cartridge I have to the levels of others in the same action.  Response?

Regards,
Sweetwater

Yes tis a logical assumption. Some would say the logic is faulty in that the brass for this rounds is not intended for use at those higher pressures. In some cases that might be correct but I suspect in most cases that's not true today. I do believe that both of those cases do in fact have adequate strength for what you propose. Am I recommending to you that you do that? Nope I'd never do that. If I had a rifle so chambered for either say a strong bolt action would I personally do it? Yup. In fact I've seriously considered a Remington Model Seven MS in .35 Remington to do just that.

The 6,5x55 is just long enough to be a bit of a problem in a short action rifle with heavy bullets so to me the tiny gain it could give you in such over the .260 doesn't justify using it over the .260. Besides I really bought my Rem. Model Seven CDL in .260 Rem. to use specifically with three bullets only: Hornady 129, Nosler 125 PT and Nosler 130 AB. I have however also used it with the Nosler 120 BT and Nosler 100PT that were not in my original plan. It really likes both those in Nosler factory loads. My entire reason for this rifle was adequate performance for deer with a bit less recoil than my much loved 7-08 with 140s.


Bill aka the Graybeard
President, Graybeard Outdoor Enterprises
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I am not a lawyer and do not give legal advice.

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Offline FW Conch

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Re: CUP = PSI cart?
« Reply #32 on: April 09, 2008, 03:47:21 PM »

   I'm not 100% sure but I think in the case of the 6.5x55 SAAMI &  the factory loaders fear the round may be fired in old surplus rifles

   that can't take the pressures  the round is capable of producing in the hands of reloaders.  Sort of the same principal that kept the

   280 second to the 270 for so many years because it was originally designed for autos & pumps. ?  Jim

   -
Jim

Offline Sweetwater

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Re: CUP = PSI cart?
« Reply #33 on: April 09, 2008, 08:32:14 PM »
Yes, there are a host of cartridges that SAAMI and factory ammo have kept to less than stellar performance due to those rounds having been chambered in weaker actions than what are built today. That's probably not all bad, considering the legal society we live in today and the fact that a huge percentage of our society do not want to be held liable for their own actions.

However, for those of us who choose to be responsible for what we do, we still have SAAMI and the manuals for 'guides'. We also have a tremendous group of professionals who are willing to share their expertise in the guiding department. None of this becomes 'law', it is all still guides. The weapon of inquery remains the 'law' and it will dictate what it likes and doesn't like - and it won't like having its pressures sent into the twilight zone. My 8mm Mauser Persian Carbine had a sizing die problem that we diagnosed as a 'short barrel-slow powder' problem. When I sent a case full of 'too fast' powder down the barrel, the report was nothing short of eirie, extraction was normal, but the spent primer fell out on the ground. I didn't need to shoot a 2nd round to recognize I'd gone overboard. A new sizing die (which an article in a gun magazine indicated might just cure my symptoms) solved my problem and I went back to 'normal' powders. This 8mm mauser Persian Carbine runs right along beside my Dad's Remington 700 30-06 without the slightest hitch. Not terribly interested in what SAAMI has to say about either of these fine calibers - we choose not to Max out either one. The '8' runs a 185gr Remington Corelok right near 2500fps out of its 18inch barrel. The '06 sends its 180gr Sierras and Noslers just over 2600fps from its 22inch barrel. Factory 180's clock just a tad more at 2640fps avg. from this '06 at 3500 ft elevation and 88 degrees F. Both weapons knock down Elk at over 250 yards with aplomb, though we frequently take them at under 100 yards. These loads are our self-imposed limits as opposed to Max for the cartridge or weapon. Granted, we understand also that different powders will run equal velocities at very different pressures. We must stay totally aware of where we are in the process, but the weapon gets the last word in raw performance. We get to choose where we operate on the scale. I choose to run my 8mm case overal length at 3.30 inches, when the chosen bullet will allow it. Vastly different than the book COAL which is usually 3 inches or less. Why? My rifle likes it. It likes loads which can be found in the 8mm-06 data, which also has a COAL in the 3.3inch area. No, they don't end up with the same case capacity, so they can't just be blindly accepted as equals, but slowly working up from a chosen starting point will guide me into what my rifle likes. And I shoot it and shoot it and shoot it. I know what it sounds like and I know what it feels like. And when it goes over the top, it tells me, on no uncertain terms. It is an entity unto itself that I have learned to understand and 'listen to'. Doesn't happen overnight.
This particular rifle came to me in 1963, and is still my go-to rifle of choice for everything on 4 legs heading for the freezer.

Regards,
Sweetwater
Regards,
Sweetwater

Courage is being scared to death but saddling up anyway - John Wayne

The proof is in the freezer - Sweetwater

Offline EsoxLucius

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Re: CUP = PSI cart?
« Reply #34 on: April 10, 2008, 06:48:15 AM »
Quote from: Sweetwater
My question on pressure has always been, since SAAMI did not manufacture my weapon, and XXX Inc makes it in a 260Rem, a fairly high pressure round, why am I limited to say 3/4's of that pressure because mine happens to be chambered for 6.5x55 or say a 35Remington? What am I missing here? Seems like I don't need to buy another rifle, but to simply upgrade the performance of the cartridge I have to the levels of others in the same action.  Response?
The problem might be determining when you have reached the new performance level without load data that takes you there.  Although there is some 6.5x55 load data that exceeds the 6.5x55 SAAMI limit of 45,000 PSI there is none I've found that takes the 6.5x55 to the SAAMI limit of the 260 Remington of 60,000 PSI.  Almost need a strain gauge.

One could also ask, well if the 270 Winchester can go to 65,000 PSI, if used in the modern bolt action rifle why not take all cartridges based on the 30-06 .471" case head to 65,000 PSI?
We learn something new everyday whether we want to or not.

Offline FW Conch

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Re: CUP = PSI cart?
« Reply #35 on: April 10, 2008, 10:50:44 AM »

   Apparently "no one" can stop you !  I just hope I recognise you if your close to me on the range !  :-[ :-[ :-[

   -
Jim

Offline steve4102

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Re: CUP = PSI cart?
« Reply #36 on: April 10, 2008, 01:40:32 PM »

One could also ask, well if the 270 Winchester can go to 65,000 PSI, if used in the modern bolt action rifle why not take all cartridges based on the 30-06 .471" case head to 65,000 PSI?

  Exactly!  No reason at all why the 280 and 30-06 should be limited to 60,000 PSI or less in a modern rifle while the 270 is running at 65,000.  The 270, 280 and 30-06 are all very capable of running at the same pressures in a modern action. 
 

Offline stimpylu32

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Re: CUP = PSI cart?
« Reply #37 on: April 10, 2008, 01:46:17 PM »
Ok guys , this is getting to be too much of a What If or Will It type of subject , so before someone gets pissed or worse HURT , lets give it a rest .

Stimpylu32
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:D If i can,t stop it with 6 it can,t be stopped

Offline EsoxLucius

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Re: CUP = PSI cart?
« Reply #38 on: April 11, 2008, 05:14:32 AM »
Exactly!  No reason at all why the 280 and 30-06 should be limited to 60,000 PSI or less in a modern rifle while the 270 is running at 65,000.  The 270, 280 and 30-06 are all very capable of running at the same pressures in a modern action.
Again, the problem is how you would determine those higher loads if there is no reloading data to support it.

Always follow published reloading data and accepted reloading practices.  To do otherwise one is no longer a reloader but has become an experimenter with all the risks that entails.
We learn something new everyday whether we want to or not.

Offline Lone Star

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Re: CUP = PSI cart?
« Reply #39 on: April 11, 2008, 06:59:34 PM »
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For example: I talked to TC some time ago about building a 307 WIN on a contender action and they said no because it could be hand loaded to to high a pressure yet they made a 375 WIN which was either the same or a tad higher that the 307. That makes no sence to me. Could not the 375 be loaded to a higher presure also.

You are forgetting the main limiting factor with break-open actions - case head thrust.  This is determined by multiplying the chamber pressure times the internal case area that the pressure works upon.  The .307 WCF has too much thrust even in factory loads for the Contender.   The .375 can be loaded to the same pressure as the .307 WCF, but it will still not produce near as much thrust.  It is the thrust that limits what the break-open actions can handle.  It makes perfect  sense.



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