Thread: Resizing .375 cal projectiles to 9.3mm

Resizing .375cal projectiles to 9.3mm

Not hard to make your own die. Use a .222 or .223 full length die and just cut it down / drill it out so the exit is exactly 9.3mm. You need to be exact and straight – use a m35 or preferably higher 9.2 or 9.25mm drill bit (buy them from China on AliExpress – get the good quality bits only). The die is case hardened, so you need to heat it first or it may be too hard to drill. After drilling hone the die to 9.3mm with fine emery paper – you want it super smooth and uniform so be prepared to put in the effort. Just use a commercial 9.3mm bullet as your guide to the exact size – it must be tight as the bullet will spring back a micro bit – constantly measure with a micrometer (I use micrometer accurate to .001mm). Case harden the die again afterwards (I heat until red all over and then drop into a tin of sump oil – seems to work). Mount the die in the press. I used a bolt with the head ground to 9.2mm to push the bullet through the die.

The big secret is the lube. None of the commercial lubes will work well – you will end up breaking things. Make your own lube from a blend of 60% natural bees wax (about $20/kg on trademe) and 40% neatsfoot oil (Bunnings sells 1 litre bottles). Heat the bees wax until liquid and stir in the neatsfoot oil. Let it solidify and give the projectile a liberal coating. Use a sharp stroke on the press.....and Bob’s your uncle....one 9.3 projectile! This lube works very well and is as cheap as chips.

I only resized Speer .375 cal 270gr btsp and Speer 235gr projectiles. I don’t think it would be possible to resize FMJ or solids. The 270gr projectiles gave better accuracy, had a high BC and performed well – they are softer than the Speer 9.3 270gr Hot core projectiles and expand more readily.

What accuracy different was there between the resized 375 bullets and the factroy 9.3mm bullets on the target?

A few variables here. The factory 9.3 270gr Hot core appeared to have the edge by a small margin over the resized .375cal BTSP 270gr with the load I was using. The difference being about 0.5" at 100m, however, this may be a function of the powder load, seating depth, or just my ability. Other rifles may give different results.

Originally Posted by Waimahana

A few variables here. The factory 9.3 270gr Hot core appeared to have the edge by a small margin over the resized .375cal BTSP 270gr with the load I was using. The difference being about 0.5" at 100m, however, this may be a function of the powder load, seating depth, or just my ability. Other rifles may give different results.

So there Bullet size dies don't do the same?