Get a 300 H&H sizing die.

Anneal the 375 brass.

Apply case lube.

Size in one easy stroke to 300 H&H.

Check case length.

Ready for fireforming in 300 Weatherby.

Picture is 375 H&H flanked by formed 300 H&H cases.

Are we also going to see what the fire-formed 300 Weatherby looks like ?

Are we also going to see what the fire-formed 300 Weatherby looks like ?

Once the license comes through, sure.

Are we also going to see what the fire-formed 300 Weatherby looks like ?

Once the license comes through, sure.

That double radius shoulder has always fascinated me

Double Radius Shoulder

Some other fascinating Weatherby stuff ...

Unknown ( to me) WILDCAT cartridge General Ammunition Discussion

I like those Ackley cartridges ...

Apparently head-spacing on the Weatherby more difficult than the normal bottle neck cartridge ?

Headspace is on the belt, so not sure why headspace is a problem.

The problem of too long brass can be confused with headspace because of the case head seperation that occurs with belted reloads if the brass is not trimmed.

If the case is too long the neck is pinched in the leade. Firing stretches the sidewall, repeated firing without trimming will cause case failure.

I've loaded a lot of belted magnum brass, headspace was never a problem.

Headspace is on the belt, so not sure why headspace is a problem.

The problem of too long brass can be confused with headspace because of the case head seperation that occurs with belted reloads if the brass is not trimmed.

If the case is too long the neck is pinched in the leade. Firing stretches the sidewall, repeated firing without trimming will cause case failure.

I've loaded a lot of belted magnum brass, headspace was never a problem.

A number of people head-space off the shoulder not using the belt
Obviously the belt is there and you cannot do anything to change that datum
The case will however expand to butt up against the shoulder
A "perfect" fit is when the belt and shoulder are in harmony
The case fits nicely and firmly without too much ( any ) play and does not "stretch"
One sizes to maintain this "harmony"
At least that is the way I understand it

I see that another issue with belted cases is not mentioned. trimming case length too short.
When a belted straight wall case is trimmed with excess clearance, it stretch's very fast and case head separation is accelerated. I suppose neck splits will be the result with a shouldered case. 

I see that another issue with belted cases is not mentioned. trimming case length too short.

I do not see how that can be a problem - with bottleneck belted cases ?
Belted bottle neck case head-spaces off the belt ( and the shoulder if set up that way )
Some rimless cases head-space off the front of the case = pistols
Case length / neck length must be shorter than the chamber otherwise there is a constriction at the neck of the chamber and excessive pressure

When a belted straight wall case is trimmed with excess clearance, it stretch's very fast and case head separation is accelerated. I suppose neck splits will be the result with a shouldered case. 

Belted straight wall case I think that there is only one = 458 Win Mag
BUT
It still head-spaces off the belt
Yes in that case the brass will flow forward in the neck to fill the chamber ( after how many firings ? )

Please correct me if I am wrong ..

When a belted straight wall case is trimmed with excess clearance, it stretch's very fast and case head separation is accelerated. I suppose neck splits will be the result with a shouldered case. 

Belted straight wall case I think that there is only one = 458 Win Mag
BUT
It still head-spaces off the belt
Yes in that case the brass will flow forward in the neck to fill the chamber ( after how many firings ? )

Please correct me if I am wrong ..
***************************
4 firings and a case is done. I learnt the expensive Way with the .458 2 inch

When you say the case is done, where is the failure? Cracked neck,  head-case seperation?

375 Weatherby cases - will they work to convert to 300 Weatherby?

https://www.jaracal.com/viewtopic.php?p=917391#p917391

When you say the case is done, where is the failure? Cracked neck,  head-case seperation?

Case head separation mainly - next cracked neck if case goes past 5-6 shots. Both issues reduced by proper proper col