RogerDat
07-05-2015, 03:44 PM
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.
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.