Figured one of you guys here may already have ALL the answers. I have BenchMark Barrels chambering up a barrel for me in 450 Remington Ultra Magnum. My question is. How do I go about supplying this cartridge with cases?????

Neck up .375 Ultra Magnum brass? If so how do I go about it? Several steps with several progressively larger expander mandrels? Do I anneal the casings before I start necking them up?

Use the parent case 404 Jeffery's? Is this possible?


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SMACK,

I made the 450 RUM for my collection on my own,necking up a NEW 375 RUM case BY HAND..no tools involved.
I just loaded it with .375 , .400 , .416 , .439 and then .458 bullets.
RUM brass made by Remington is soft at the neck area,I didn't need to anneal the neck.
Case formed quite easy without cracks
Obviously using a couple of progressively larger taper expanders should be a easier work...

From left to right:

7 mm RUM ( commercial)
300 RUM ( commercial)
8 - 300 RUM
338 RUM ( commercial)
338 - 300 RUM ( 338 Edge)
358 - 300 RUM ( 358 Towsley)
9.3 - 300 RUM
375 RUM ( commercial)
416 - 375 RUM
458 - 375 RUM

In the same way I made also the 358 - 338 RUM and the 9.3 - 338 RUM

That's cool.

Rich
DRSS

Smack

You are not going to have an issue going from 375 Ultra up to 458 in most cases. There are several ways to get there.

First way, and what I would check first and foremost. I assume die sets are available from probably RCBS and Redding for this one, maybe Hornady too. I think you may be able to use the size die and expander to go from 375 to 458 without much issue. Use some lube inside the neck of course. I have had no issues at all going from 300 to 358 and 366 with 300 RUMs. Most likely you may be able to do the same without splitting necks. Get a tapered expander for the size die. One thing to be extremely careful about is setting the shoulder back to far with this 375 RUM brass. Do that, gives room for the case to move forward too far, and you will notice a ring about 1/2 inch above the pressure ring, the case is going to split at that ring within a few firings. So make sure that first firing you bump that shoulder a bit when chambering.

Now you can also have the die makers make an expanding die. Long, tapered rod that will take it from 375 to 458 in a separate step to begin with. In most cases this works fine, and going from 375 to 458 it should work great without splitting necks.

Third, drop 15-18 grs of Bullseye in the case, toilet paper on top to hold the powder next to the primer, stuff it full of cornmeal to the top, pack it slightly, top it off with toilet paper to hold everything together, go outside and fire it in your rifle chamber in a safe direction. Instant 450 RUM. This is a bit of a chore, but you get a really good start on the brass.

Now how do I know all this? My own 500 MDM is done the same way, only I have to go from 375 RUM to .500 caliber. I had Hornady make a tapered die and that works pretty good, but I found myself loosing about 25% of the necks due to splitting on a soft batch of 375 RUM. One batch I run was perfect, 100%. So I fell back on the corn meal bullets and got that up to 95% good to go brass on that soft batch. I have to go a long way from 375 to .500.

Do you have dies yet? If so give the size die the first chance, it will probably work fine. Tapered expander.

Good Luck

Michael

called 458 ultracat
http://www.z-hat.com/Ultracat.htm

my 416, 458, and 470 ARs can just form rum brass, if you set them long.. but i use 375 rum for mine, to neck up easier

Seeing that I already have a set of RCBS 450 Ultra Magnum dies, I grabbed a once fired .375 Ultra magnum case. Gave it a good rub down inside the neck and out with Imperial Wax. The number for RCBS already set on speed dial just in case I crashed the tapered expander in my 450 Ultra FL sizer die. I gave the press handle a good firm stroke and BAM!!! One perfectly sized 450 Ultra case...... Pleased to say the least.


450 Ultra on the left as compared to the .375 Ultra Mag on the right.




Now for my next question, I plan on shooting the Nosler 500gr Partitions. What would be a good powder choice and powder charge to start at?


Thank you gentlemen, for your input.

Smack

Excellent! I figured you would do just fine doing that and be ready to go! Careful with the shoulder too, don't set it back too far when sizing for that first fire forming to the chamber. Don't do a bunch until you have rifle in hand to see how they chamber, you want to feel that little bump when you lower the bolt.

I know, I have split a bunch in my day! Recently with the 500 MDM and 375 RUM brass.

Good show, it looks great.

Michael

Michael,

I kept that in mind and left the FL die a good 1/4" inch plus off the shell holder.

Any suggestions as for powder selection or beginning powder charges using a Nosler 500gr Partition?

Smack

I will check around and see what I can come up with. Seems there was some sort of article a few years ago about a 458 Ultra. I will see what I can come up with. I suspect RL 15, IMR 4064 and H322 would be a good start.

Michael

DELETE

Your 458 Ultra has a case capacity a bit over the 458 Lott so you could use Lott data and work up...I would do that to start with and then see what others come up with for their rifles and go with the powders Michael listed starting with RL-15 or Varget.

Sometimes it is better to fireform with cream of wheat or grits, in the chamber, rather than using a press expecially when sizing UP...I've had less case, almost zero losse, that way...going down you HAVE to use a press.

FooBar

Correct, Varget would be a good one to start too. I could quickload it, but it is not listed in my list of cartridges, so I have to input it and have not had time to do so yet.

Michael

There are several powders that will work with the case capacity of the 450 Ultra, and it is on the edge as to which one is "best".

AA2520 and AA2700 are good powders if you like ball powders.

Varget is just a bit faster than RL-15 on the burn charts, but it depends on several factors as to which way either will jump.

I would need to know the actual case capacity(if it were my shooter) before deciding on a powder to begin with.

The 450 Ultra will definitely be a very good "tweener"...in between the Lott and the 460 WBY....pretty close to the 450 Dakota also.

Luck

Thanks gentlemen...

Well I'm down to the wire on the 450 Ultra project. I can't make up my mind on the barrel length? I want to go as short as possible, what do you gentlemen figure would be a reasonable length?


Thanks...

26 inches and a hacksaw come to mind.
What bullets would you use?
What powders?
Target velocities?

I plan on shooting the 500gr Nosler Partition and the 500gr Barnes X. I planned on using RL 15 and VArget. I have no idea as velocities, figure I would start with .458 Lott load data and work up.