Does the brass know the difference?

[Ray B]

When developing loads I follow the method used by Ken Waters using case expansion at the web as an indicator of maximum safe pressure. If possible I use brass from the same company (previously Winchester, but others now seem to be of higher quality) so that the indicators will be uniform. The rifles involved are all of strong modern actions so the weakest link in the equation is the brass case. So I'm wondering if the limits SAAMI and CIP place on cartridges is valid. In particular I note that several African cartridges have lower limits than other magnum and even standard cartridges. the reason given is that some are to be used in break-action doubles that are not as strong as bolt-actions and that if carried in the heat of Africa, the powder is susceptible to increase burnrate and raise pressure. But what about cartridges that will be fired in a modern bolt-action in a cool climate or using powder that is not temperature sensitive. For example, the 458 Win Mag has a CIP limit of 62K while the 404 Jeffery has a CIP limit of 53K. So if both are chambered in a CZ550 or similar and the 458 is considered safe at 62K, wouldn't the 404 also be safe at 62K?

 

[Shootist43]

Good question/observation. I'm waiting to see how others feel about this. Have you looked at some of the various hand-loading forums to see if this question has come up before?

 

[greyfox]

Ray, In certain applications, certain rifles/actions, then yes, absolutely.
That's why you start working up slowly and check for signs, etc.

Be advised, I've personally been in a situation where my loads were perfectly safe at home when and where they were loaded but going to a warmer climate increased the pressure where I had to back off a grain to 1.5 grains.

Also, it's not always the action, sometimes it's the brass (.30-30 Winchester). The 7X57 is notoriously under rated, as is the 45-70. Information is available for mild loads for older/weaker actions and modern/stronger actions.

Now, ask yourself: Is it really that important to gain some velocity at the risk of damaging or destroying a rifle or trying to deal with a stuck/ruptured case? Some very smart people develop load data under controlled conditions - I'm pretty sure they are smarter than I and have much more precise equipment/conditions: therefore I do not recommend exceeding max loads.

What's perplexing is comparing various loads from different manufacturers - I shoot a 7mm rem Mag and the books/net are all over as to haw much powder and what velocity.

Load to an accurate/safe level, shoot over a chronograph and compute.