That might have something to do with why Marlin isn't offering the chamberings any more. Actually, the PSI conversion is more to the order of 60.9K!
The 356 Win was designed to the same pressure limits as the 358 Win. Knowing the lever-action design wasn't up to the those limits, Winchester used thicker case walls to contain the pressure and that is why the case capacity isn't the same as the 358 Win. Same story with the 307 vs. 308 (62K... what was Winchester thinking!) and 375 vs. 38-55.
Most argue that you can't convert CUP to PSI and PSI to CUP. Not so, the problem only stems to lack of a standard in collecting early CUP data. The calculation is:
CUP to PSI:
PSI to CUP
These formulas are formated so that you can paste them directly into a XLS spreadsheet. Just insert a cell address over CUP or PSI. Here is a link to a paper on the formula: Correlating PSI and CUP by Denton Bramwell
It will be interesting to see what happens to some of the numbers as SAAMI re-evaluates the standard from CUP to PSI. Look at the 35 Rem... it actually gained some thump! Enter the 35 Rems CUP of 35K into the formula, it converts to 32.8K CUP. The new PSI reference is 35.0K PSI. Same story with the 30-30 Win. The 444 Marlin lost a bit.
I've been working on a pressures chart, but it is not very complete as yet with regards to modern cartridges. My interests lie with the older, rimmed cartridges. Unfortunately, I do not have access to the most up to date SAAMI information, eg. modern .405 WCF. The book they sell is over 10 years old, and it does not include many cartridges. I don't believe they keep the printed copies up to date; you should try the CD version. I have more information on the standards from Europe's CIP, which is SAAMI's counterpart there.
That formula isn't too reliable as there's some significant outliers when you apply it to enough common cartridges. The .284 looks like the biggest one yet, but the .270 Winchester and 7-08 Remington are outliers too, and in opposite directions. See the chart I worked up in this old post. http://www.shootersforum.com/showthread.htm?t=8512
There is some intresting reading on this very topic in the september Shooting Times. Ken Oehler the guy who makes crono's and such has just signed on to do a monthly column. His first writing is on this very subject! you may can access this from the net.
I was wanting to know about the .325 WSM. COuldnt find it anywhere. So I looked in all the reloading info I could find. None of them seem to go above 64k psi. Seen one dead on 64k, but never above. So Im guessing the .325 WSM is probably maxxed at somewhere between 64k and 65k.
Interesting, but I wonder how many know why they set certain pressure limits on certain cartridges?
The answer is simple and complex at the same time. The specs have to be set, per cartridge based on their best evaluation, to match the weakest existing action out in the field that are still being used.........and that takes some doing!
Good examples of this was the specs on .257 Roberts (many in early Spanish actions brought back from the Spanish/American War) and 8mm Mauser (many 1888 rifles with smaller grovres).
Dixie Slugs ran into this early, since the specs are low on the 12 ga 3" Mag. It is interesting to see the specs on the 12 ga 3 1/2" Mag vs the 12 ga 3" Mag........with both on the same frames.
Then things got real complicated in certain 12 ga specs since there are now rifled shotgun barrels! Take the example that there are now rifled shotgun barrels on rifle actions lke the NEF rifle actions that can have 280 Remington barrels sent from the factory.
So.....The gun and ammo co's have to deal with all this, including shotguns the have front locking lugs locking into the barrel extension (very strong) vs older models with rear lugs locking into the frame (not so strong).
Because of the reasons above the specs must be on the ultra conservative side......something to think about?
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