Magnum primer Vs standard primer in .357


January 25, 2008, 06:20 PM
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.

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.

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January 25, 2008, 06:24 PM
The primer shouldn't make that much difference with 2400 or Blue Dot powder. Maybe Alliant used a test barrel with a universal receiver (no cylinder gap) so they could use a strain gauge to measure the pressure, and Speer used an actual revolver.

January 25, 2008, 06:32 PM
The Gold-Dot is a plated jacket bullet and is softer then a Cup & Core bullet so might slightly use more powder safely.

Speer data is usually hotter then Alliant, even when not using Gold-Dot bullets.

Regardless, I would have to consider 14.5 grains of 2400 with a 170 grain bullet of any type a maximum load in the .357 Mag.

I think standard primers will do nicely with 2400 powder in the .357.
That is all I've ever used for close to 50 years now and I have never had a problem.

evan price
January 25, 2008, 07:14 PM
I use nonmagnum primers unless I am making hot loads.
The thickness of the cup is greater on magnum primers I was told. Also a little hotter for large charges of bulky powder.
I haven't had any ignition problems.

Peter M. Eick
January 25, 2008, 07:37 PM
If you look back through the loading books folks have gone back and forth on the mag primers for 2400 and the 357mag. The current wisdom in my manuals is to NOT use magnums and to use standards. I am still loading magnums for 2400 but next batch I will try non-magnum primers and test them.

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