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Old June 12, 2012, 01:55 PM   #10
Clark
Senior Member
 
Join Date: December 4, 1999
Location: WA, the ever blue state
Posts: 4,678
CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.
Quote:
rebs I have the Hornady 45th edition book, is it safe to reload the factory duplicate loads ?
When they state maximun load, is there a cushion built in there, is it safe to load a max load ?

Razor thin margins:
The cushion is as small as they can make it with 270Win, 6mmRem, and 22-250 Rem. At 65 kpsi SAAMI registered max average 84.5 kpsi - 91 kpsi proof loads, the case head of these cartridges is on the edge. They use the 1889 7.65x53mm case head, and when built with a large Boxer primer pocket, it is possible for me to load at 67 kpsi for one rifle and have enough safety margin to allow for variations in components, my reloading process, and temperature.

Bigger margins:
The 260 Rem was registered with SAAMI at 62kpsi.
I can't help but think the thin margins of the 270, 6mm, and 22-250 were making problems with factor ammo in factory rifles.
I load it at 67 kpsi, for obvious reasons.

Even bigger margins:
The .223 Rem is registered at 55 kpsi, and I load it at 75kpsi and get long brass life.

Even bigger margins:
If someone gives me a another 25acp that I have never seen that make or model before, if I see it is made of thick steel, good firing pin to firing pin hole fit, and good case support, then I will start the work up at double max book loads, and probably end with my maximum usable load somewhere around 2.5 times the maximum published book load.

What does it all mean?
There are tiny margins [cushion] in guns and cartridges and then there are huge margins, but where they are is a secret.
If the information got into the hands of ordinary consumers, they might hurt themselves.
And there is big money in overloading a cartridge and giving a new name.
To find out where the margins are exploitable, you must know the secret handshake, to design new guns and new cartridges.
That is what I am doing today, designing and building gun parts for a wildcat.
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