225 grain lead load for .375 Win

B

Boox

New member
Anyone here loading for this almost relic? I'm looking for loads using a 225 grain lead slug. Powders on hand are RL 15, H4350, H-380, BL-C2, Varget, IMR 3031 and 4064. Have seen some loads with 2400 also, mostly for 38-55, which I read will probably work OK. Other powders are available.
Appreciate any insights, thanx,

Boox
 
Welcome to the forum.

Those powders mostly look too slow for a nearly straight case with only 0.229 bullet sectional density. Even for a 249 grain cast bullets, the Lyman manual shows all powders slower than IMR4227 requiring compressed loads, and that sectional density is higher at 0.253.

Basically, the lower the sectional density, the faster a given pressure makes the bullet run away from the chamber. The straight wall shape generally has smaller powder space relative to bullet diameter, and that means the bullet doesn't have to run very far before the space the powder is burning in has doubled. Both those factors mean the powder has to burn faster to make gas fast enough to keep pressure up as the bullet moves forward.

The load data for the 249 grain bullet is 22 grains of 4227 to start and 26 grains maximum. That should be plenty safe with the lighter bullet. It should come up at around 2000 fps, which is probably about as much as you want to do with cast bullets until you become more experienced with them and developing loads of your own for them.
 
For somewhat of a reduced load with the .375 Win, I use a max load of Trail Boss powder with a 255 gr cast bullet. The same powder charge should be good with the 225. From the powders you have on hand, the Lyman manual shows 27 to 31.4 gr 3031 with a 249 cast bullet. 20 to 24 gr 2400 are shown for the same bullet. Max load with Trail Boss powder means filling the case to where the base of the bullet will be seated. 4227 loadings from Lyman are shown above with the 249.
 
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"...this almost relic..." It was introduced in 1978, but it, like many cartridges, is the answer to an unasked question.
Not seeing cast bullet data anywhere(my manuals are older than it) , but 220 grain data would be close enough. Five grains won't matter.
 
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