357 mag load

According to a very old site


Herco From 9.6 grains to 11.5 grains
CCI-550 Primer

Of course start low and work up and chrono everything.

Use at your own risk.
 
2008 lee, with a 125g jacketed bullet
herco
start 9.0 at 1473fps
max 9.8 at 1590fps and 33600psi

my 2021 lee manual no longer lists that load
my lyman manual has no data for that bullet and powder
my speer manuals has no data for the bullet and powder
alliant lists no 357 mag data with that powder.

based on the burn rates should be ok in 357

you didnt mention plated or lead. lead does not like to be pushed over 1100-1200fps without gas checks.
 
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Reference your manuals .... Look under .38 Special... You might find more data there. No reason to load so 'hot'. I tested 5.0g (890fps) to 7.5g (1140fps) of Herco under a 158g SWC in .357. Herco doesn't need a magnum primer. I don't use/load the ultra light 125g bullets. You didn't say if the 125s were lead, plated, coated, or jacketed or style.
 
I am using X-treme 125gr bullets. Have been using them for years with various powder and get good accuracy. Tried 9.1 gr Herco and got flattened primers. Would like to know how low I can safely go? Cannot find any info for 125gr bullets with Herco.
 
sticky extraction? flattened or flowed primers? most of my primers flatten a bit, usually a sign of a good max load for me. however if its flowed, like filling up the entire primer pocket its time to back off. thats how I do it anyway.

If you not comfortable with the load, what I would do in this circumstance, is back off 0.5g and test again, say 8.6g and see how things act.
 
Poconolg, I checked my "library" of manuals for .357 loads

Hornady Vol II 1973 does not list Herco with 125gr, but does list it for 158gr (start 6.5gr -800 fps; Max 9.5gr - 1100 fps)

Hodgdon 25th Ed 1989 - NO Herco for 125gr or any bullet weight listed

Hodgdon 26th Ed 1994 - Same as 25th Ed

Lyman 43rd Ed 1964 -No Herco listed for any bullets

Lyman "Ideal" handbook #38 1951 - only bullet listed is 156gr Lead and no Herco listed.

What is your reason for using Herco if you've been getting good accuracy with other powders for years?
 
Older Alliant data lists 9.8 Herco max with a 125 jsp, less 10% for starting would be 8.8 grains.
The only other data I have is Sierra, 9.6 start, max 11.5 with a 125 jsp.
I would be comfortable working down from 9.1 in .2 increments until you find a load you like.
 
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Looking at .38 Special, the loads I found was Herco 5.6gr to 5.8gr under Jacketed 125g Bullet. So you can go at least that low. I'd start at 6.0gr and work up. Looks like your range is from 5.8 to 9.8 (from above data) . Plenty of room to play as Herco is not pressure sensitive. As I said above you don't have to load 'hot'. Enjoy.
 
Herco load

FWIW

Speer #8 (1970)
.357 Mag
speer cases
CCI 550 primer
Speer 125gr Soft point

Herco
10.0gr 1245fps
11.0gr 1305fps

test gun S&W Model 27 6" twist 1-18 3/4
 
One Book/One Caliber copyright 2000

Are the Extreme Bullets copper plated or metal jacket?
Copper plated are different in the friction department, so consider that.

38 Special...125 gr. Nosler JHP....4.9--5.9 grains

357 Magnum
125 gr. Sierra JSP.....9.6--11.4 grains

There was data for Lyman cast bullets using Linotype 150 gr starting at 6.2 and max of 7.8.
 
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