The "Lawyerfication" of Reloading Data

[dleong]

I downloaded the latest edition of Western Powders' load data manual (version 5.0, available here) and compared the data against a previous edition (version 3.2.2) of their manual that I had used just a few years ago to develop some .357 Magnum loads for my 6" Ruger GP100. The following image shows the pages from both manuals for .357 Magnum loads using Accurate No. 9 powder:

(Version 5.0 is on the left, 3.2.2 the right. Click on the image to view the full-sized version.)

You can see that the loadings using the same projectiles have been significantly reduced in the current version of the manual. Of concern to me is the highlighted load; I had used the data from version 3.2.2 of the manual to develop my current .357 Magnum loads, eventually settling (after much experimentation) on 12.9 gr. of No. 9, with the OAL stretched out a bit to 1.61" instead of the recommended 1.58". This puts my load almost smack in the middle of the range indicated in the 3.2.2 manual.

However, 12.9 gr. of No. 9 now shows as being a full half grain beyond the maximum charge in the 5.0 manual.

The load I had developed from the 3.2.2 data is consistent in velocity, surprisingly mild in recoil for a magnum, and above all, extremely accurate. The sights on my GP100 are dialed in for that load, and I currently have about 400 cartridges loaded with that recipe.

If the data in the latest load manual are to be believed, my current .357 Magnum rounds are no longer safe to shoot. Should I be worried and start disassembling them?

[Ballinger]

Have you noticed any pressure signs?

[engnerdan]

I know this has nothing to do with the pusification of the load data it is very interesting. In that range (from the new lowest to the old highest charge) of powder charges the powder to velocity ratio is fairly linear. In fact you can almost just multiply the charge weight by 100 to get the velocity.

I have noticed that the load data in the Hornady books is very watered down. I was looking at some 308 load data and the max loads from Hornady were just about the starting loads for a same weight bullet from Hodgdon.

[cobb]

Look in some old Lyman manuals, their loads are way over the numbers you see now.

[Pat Cannon]

If the data in the latest load manual are to be believed, my current .357 Magnum rounds are no longer safe to shoot. Should I be worried and start disassembling them?

Maybe if you were shooting them in an inferior handgun like, say, a Smith & Wesson, but not in a Ruger.

[dleong]

Have you noticed any pressure signs?

Only a very slight flattening of the primer cup, but that is to be expected of almost any magnum load. The spent brass falls freely out of the cylinder, without having to use the ejector.

[JJ]

Remember also that powder formulations do change over time. This is one reason that you will see numbers that don't jive between editions.

As well, one needs to consider the test equipment being used. Test barrels do vary, from barrel to barrel. Identical barrels from one manufacturer may show vastly different readings. It is likely that when they do their testing that they use a couple different barrels, and collect/compile the data. At that point, it would behoove them to use the max data from the test apparatus that shows the highest pressure signs.

I know this is an issue that SS an I will disagree on, but the load books are reference materials. Max is just a reference number. i have had loadings that at max charge were well beyond what a give firearm could handle. i have also had loads that I could safely go 10-15% over book max, before pressure signs became evident.

[Makarov]

To compare:

From my Accurate 2001 Reloaders Guide
357 Magnum (new data)
Gun S&W 686 6 " barrel CCI 500 primer HDY case
Bullet (L) 158 SWC OAL = 1.580"
Powder No.9 13.5 gr 1499 vel

[Rip Van Winkle]

Accurate powders have a reputation for inconsistent lot to lot burn rates.

Which is why I no longer use them.