Hello Cast Bullet Experts.

I'm new at this and am working up loads for a 43 Mauser double rifle.

Have a nitro-for-black load that's working very well but running low on Buffalo Arms .446" 340 Grain Hand Cast Lead Bullets, which remain out of stock. I'm on the email list for when they get back in stock.

I've done a cursory search through castboolits and am gaining knowledge.

How far down can one size bullets through a die? I'd love to buy .458 in a close weight to 340 grain and squeeze them down to .446 if that's possible.
Can you size a lubed bullet, or start with a non-lubed and add lube?

I have a very well used rock chucker setup.

Any advice is appreciated and have enjoyed reading many of the threads in this part of accuratereloading. thank you

Not a CB expert but have cast and used lead bullets for a long time.
The normal sequence is to size then lube. A cast bullet lube/sizer such as the Lyman 450 sizes the bullet then the lube is pumped into the grooves.

Sizing bullets down will be limited by the purchasing power of the sizing press being used and the need for retaining a reasonable depth of groove/s for the quantity of lube needed during the passage down the bore.

The dedicated cast bullet lube/sizers such as the Lyman, RCBS, etc., are not built for sizing bullets down calibres, they are generally built for sizing bullets a few thou down from as cast to about a thou over bore size.

A reloading press with sizing dies will certainly have the purchasing power to size any cast bullet down but again the process will be limited by the depth of grooves left after sizing to hold lube. Over sizing usually sees lead slough off into the grooves leaving no room for lube.

For that drastic of a sizing down you should do it increments, which in your case is going to take a few dies of different sizes. Best to use a luber/sizer as you won't lose your grooves as much as you would in a push through Lee type sizer which is used in your reloading press.

You might be better off finding a mold that will drop them close to the size you are after. Accurate Molds can custom make you a mold and also if you get on Accurate Molds website and go through the molds that already exist you may find what you need.

https://accuratemolds.com/

I’m far from a cast bullet expert, but I routinely size more available .511-.512 cast bullets (not gas checked) to .505-.506 for my .505 Gibbs with a single homemade sizing die in a Rockchucker press, not at all hard to do. I then tumble lube them with Lee Alox bullet lube, works pretty well.

I haven't used my luber/sizer for decades.

I have switched to lee push through dies.

Alox or powder coating for lube.

One can size down until you have no groves left if you want.

For powder coating one doesn't need any.

I have polished out the Lee dies to most any caliber you want.

Powder coating could very well be the solution to your problem.

How about these two bullets, Accurate has them on their catalog. Pretty dang close to your size:

https://accuratemolds.com/bull...l.php?bullet=44-340B

https://accuratemolds.com/bull...l.php?bullet=44-340C

Gentlemen,
This is very helpful, thank you.

shootermetal, the first link looks exactly like what I'm shooting now, thank you.

Will look at Alox and powder coating.

The plan is to shoot this gun a lot, have a decent amount of brass but going through bullets too quickly, which is a good thing!

I have some Hawk 400 grain but will try their 350 grain as well.

Much appreciated!

Glad I could help a fellow shooter.