Necking down magnum basic brass

[analog_peninsula]

Hi everyone,

I bought some magnum basic brass for a .375 wildcat very similar to the.375 Weatherby that I’d like to take to Africa. What’s the best way to reliably neck down the cylinder brass very similar to Lott brass in dimension to .375 caliber?

Hints, tips, and suggestions are greatly welcomed.

 

[Ray B]

the inside diameter of cylinder brass is about .47" so necking it down is reducing the diameter .05" around the circumference. this would best be accomplished in two stages. One die would reduce from .47 to .42, then another from .42 to .37". A sizing die for a cartridge such as .404 Jeffery would probably work for the first step since it has the two necessary features: the open end is large enough to accept the unsized brass and has a very gradual sizing down to .42". the only question for that first stage would be if the case is long enough to get into the sizing portion of the die to get the case reduced to .42". the final sizing die may be the actual cartridge sizing die, the issue is if the shoulder angle is flat enough that it can reduce the neck diameter without collapsing the case. If not, then another die, possibly a 375 H&H would work to size the case. the problem with that is you would want to push the case into the die just enough to reduce the top of the neck to .37 as the body of the case would be reduced more than you'd want and would be needed to be fire formed out to the wildcat's dimensions.

 

[lkydvl]

WHY NOT JUST FIREFORM IT FROM 375 H&H?

 

[BlueFlyer]

Per the advice above, but anneal the brass before and after forming.

 

[analog_peninsula]

WHY NOT JUST FIREFORM IT FROM 375 H&H?

This is international travel brass. Incorrect head stamp.

 

[lkydvl]

so how does that make Basic Belted brass any better? It will not have the correct headstamp either.

 

[analog_peninsula]

No head stamp is very different than a different head stamp.

 

[analog_peninsula]

Basic to .458 Lott no problem.
.458 Lott to .416 Remington no problem.
.416 Remington to either .375 H&H or ICL gives 50% collapsed shoulders.

Any suggestions on necking down from 416 to 375 without collapsing the case shoulder?

 

[Ray B]

It should be possible to reduce diameter from 416 to 375 without issues- my first change would be to us a die that has a very gradual slope from 416 to at least 400. I'd try a 300 H&H and partially insert the brass so that the neck is reduced but not so far that it starts pushing the shoulder in. Other dies may work- the issue is to gradually with a easy slope narrow the neck.

 

[fourfive8]

100% success? Difficult. Goal is minimal loss. Anneal neck and shoulder area. Use plenty of lube, like Imperial. Don’t try to resize in one stroke. Take small “bites”, bringing the case all the way out of die between strokes. Two things can initiate/cause shoulder collapse- mechanical friction and trapped air.

 

[analog_peninsula]

Success! Thank you for all your help. Here’s what works:

Magnum basic to 458 Lott
458 Lott to 416 Remington
416 Remington to 378 Weatherby
Trim case to 2.850
378 Weatherby to 375 ICL
Then fire form.

The 378 Weatherby die reduces the neck size without applying pressure to the case shoulder. At no time did I have to apply significant pressure.

 

[buffybr]

Per the advice above, but anneal the brass before and after forming.

Annealing the brass before forming may collapse the shoulders.

 

[farmer_john]

This is international travel brass. Incorrect head stamp.

Can you explain what that means exactly? And what does headstamp have to do with traveling with ammo?