Load differences between manuals

[Hook686]

I have a S&W 627PC, a box of Speer 170 grain GDSP's, some Alliant 2400 powder and a box of Winchester Small Pistol primers. The Alliant web site shows a maximum charge of 12.1 grains of 2400 for a 170 grain FMJ bullet.

http://www.alliantpowder.com/reloaders/RecipeDetail.aspx?title=Pistols%20and%20Revolvers&gtypeid=1&weight=170&shellid=1015&bulletid=30

Speer had listed last year on their web site supplemental reloading data for 170 grain GDSP bullets. This data showed a range of 13.9 grains to 14.5 for a 6" S&W M19.

At the maximum load, Alliant indicates the 12.1 grains of 2400 will yield about 1365 fps. The Speer web page listed about 1166 fps with 14.5 grains of 2400.

This strikes me as a BIG difference.

Speer no longer has the data page for supplemental reloading data on their web site. I printed the data page when it was posted. It also shows a maximum load of 9.4 grains of Blue Dot for about 1002 fps. The Alliant page shows a maximum of  9.7 grains of Blue Dot, for about grains 1310 fps. Here a little more Blue Dot gives quite a bit more velocity, whereas with the Alliant 2400 powder where, quite a bit more powder gave quite a bit less velocity. I do note that Alliant uses magnum primers, while Speer used standard primers.

Alliant data uses a Full Metal Jacket bullet, Speer data uses a Gold Dot Soft Point bullet
 Alliant used magnum primers, Speer used standard primers;
 Alliant used 1.585" OAL, Speer used 1.590" OAL;
Alliiant used 5.6" barrel, Speer used 6" barrel

It seems to me Alliant's use of a slightly shorter barrel (slightly lower velocity) and a sliightly shorter OAL (slightly higer velocity) is kind of a 'Trade off' when compared to the Speer slightly longer barrel (slightly higher velocity) and slightly longer OAL (slighly lower velocity). Thus it seems to me the BIG difference, 12.1 grains of Alliant 2400, for 1365 fps Vs 14.5 grains of 2400, for 1166 fps, comes down to magnum primer use by Alliant and standard primer use by Speer.

Is that even plausible ? Can anyone with Speer # 14 verify that the data shown last year on the wen page shown above is also in their new manual ? 2.4 grains more, for 200 fps less concerns me.

[Savage]

Just goes to show how much difference there can be in different guns or test chambers. The loads listed were maximum in their tests. (Another good reason not to share data with anyone.) When trying a new load, it's always best to start well below the max load. Use a chrono to check your loads and watch for pressure signs. You may find you have reached the max velocity,  along with the pressure that goes with it, long before you reach the maximum charge in any of the manuals. I have found that max "b*##s to the wall" loads are rarely the most accurate and put a lot more stress on the gun and shooter.
Savage

[Catfish]

With that much difference in velocities it sounds to me like one was using a revolver and the other a chambered barrel.

[Lone Star]

Speer #14 has the data you quoted from their website - it is the same data and the same M-19.  What you have neglected to consider is the difference in the bullets used.  Speer's 170-grain bullet is formed in a completely different manner than the bullet used by Alliant (most likely a Sierra 170).  Different length bearing surfaces and jacket/core hardness can make big differences in load data.  Note that Speer states in their 44 Mag section that bullets with a harder core result in lower pressures, hence their loading data may not "track" with loads for other bullets.  This is probably - along with different primers, cases, powder lots, test barrels, etc. - why you noticed the data differences.  Handloading is not always the 'simple task' that some seem to believe.....


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