All Data for the 500 S&W is Loaded Down


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bluetopper
November 28, 2010, 11:57 AM
I have seen where the SAAMI spec for the 500 S&W is 60,000psi and all published reloading data that I have seen is listed at 50,000psi.

Anybody else noticed this?

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rcmodel
November 28, 2010, 12:14 PM
That's true of about any caliber you want to name.

Reloading data is compiled with off the shelf powder you and I can buy.
Factory ammo is loaded with god knows what kind of powder.

But you and I will very likely not have access to the same lot number of powder at the store the lab used.

And every gun out there isn't exactly like every other gun just like it.
Every .500 S&W made isn't made by S&W.

And if you reload, you will very likely be using old tired brass at some point, even if you started out with brand new brass.

They have to error on the side of caution to cover all the variables is all.

rc

Steve C
November 28, 2010, 12:36 PM
The pressure level listed in reloading data is an AVERAGE, some rounds would be higher and some lower. No reloading manual or even factory made ammo will be loaded to the maximum SAAMI pressure for every round, their average pressure will be somewhat lower. There isn't enough uniformity between charges thrown, component construction and firearms to assure the same pressure from round to round so some safety factor must be employed to assure that the SAAMI maximum is never exceeded. This is why hand loads need to be worked up and excessive pressure signs can appear even before reaching maximum book load.

There have been more than one reloader who thought they could guess at how much more powder they could add to the book load to get this magical "maximum pressure" and have wound up with their guns in pieces. What you get for pushing beyond safety limits is generally a very marginal increase in velocity that doesn't kill paper or critters any better than a safe load.

Jim Watson
November 28, 2010, 02:28 PM
I read that the policy is to show the top load that is no closer than two standard deviations to the maximum. So the farther a published load is below the SAAMI maximum, the more erratic it was in testing.

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