357 magnum and 2400 Lyman 4th edition oddness

[RogerDat]

Looking at pages 258 and 259 of Lyman 4th edition. 357 magnum for pistol and noticing an oddity with 2400 powder. The normal progression is less powder as bullet weight goes up. The Lyman data follows this for a bit then goes wonky with the starting loads for 2400 powder.


120 gr. bullet lists either 13.0 for a round nose, 13.5 for truncated cone.
150 gr. lists 11.2 gr.
155 gr. lists 10.6


This seems normal so far. Heavier bullet = more pressure for given load = less powder starting load.

BUT THEN pattern sort of starts over ....

158 gr. bullet lists 13.2 gr
160 gr. at 11.4 gr
170 gr. at 9.7


AND then 180 gr. bullet jumps up to 11.1 gr starting load.

What struck me as odd - and somewhat confusing is:
I would have expected that a 155 gr. bullet would have a higher starting load than a 158 gr. bullet.
I would NOT have expected a 160 gr. bullet to have a higher starting load than a 150 gr.
I would NOT have expected a 180 gr. bullet to have a starting load that is both between 160 and 170 gr. starting load AND 150 gr. and 120 gr. bullet starting load.

I know the load data for 357 and for that caliber with 2400 has change over the years, having been reduced as more accurate pressure measurements have become available (and guns ended up rattling and loose from the barn burner loads) Have heard that 2400 has changed a little over the years as well but those numbers are just not very consistent with each other.

I should add that I noticed this because I have some 158 gr. SWC and 150 gr. WC rounds and seeing a lower start load for 150 than for 158 gr. caused me to look more closely when trying to develop a load using 2400 that was on the low side for power.

[Bzcraig]

You need to also look at OAL and pressure for the whole picture.

[9.3X62AL]

I have used Lyman #358156 seated and crimped into its top crimp groove with 13.5 grains of Alliant 2400 and CCI 500 caps into W-W brass for over 20 years to duplicate the W-W Super-X 158 grain JHP duty load I carried for many years. These run 1235-1250 FPS from my 686 x 4".

[roberts1]

noticed the same thing for unique and the latest lee book. Had higher starting loads for the 45 colt than the 44 magnum. I know different caliber but the 44 is a much higher pressure cartridge. Also the max load for the 44 and 240grain lead bullet is 7 grains according to lee. At that load the brass wouldnt even seal. For the 45 colt the max load was 9.5 grains for a 250 grain lead bullet I guess that is why we work loads up ourselves. All I ever look for is a safe starting point.

[RogerDat]

You need to also look at OAL and pressure for the whole picture.
Does OAL matter as much as how much of the case is taken up by bullet? Or is that what you mean by considering the OAL?I
know something like a wad cutter that sits down in the case can up the pressure. But these are not radically different bullet profiles but I can look at OAL I suppose.

[shorty500M]

Case capacity aka cubic inches MATTERS DRAMATICALLY!! Regardless of powder type, seat a bullet deeper and you decrease boiler room capacity and the pressure ramps up! Seating out longer can decrease pressures but on a much slower curve! .060 deeper raises pressures more than seating out .060 will decrease!

[Boogieman]

My standard .357 mag. load is a Lyman #358156gc over 13.5gr. of 2400 It cronys 1250fps out of a 4 " Ruger with very low S.D.s RCBS 162gr gc works well with this load also. This duplicates most factory 158gr loadings. 2400 needs to be loaded to normal pressures to burn clean.

[Larry Gibson]

Does OAL matter as much as how much of the case is taken up by bullet? .

The seating depth is indeed what you should consider as it governs the functional "case capacity". Unless the bullets have the same length from the base to the crimp groove the OAL is meaningless.

Larry Gibson

[MtGun44]

Yep, what Larry said.

Write that on the wall in large block letters.

Bill