Although the RUM case has a rebated rim, is there a difference between the two in base diameter? I know that the RUM is .550 @ the base. I have looked at some websites and found a base diameter for the .404 of .544. Just a little confused since the RUM is supposed to be made from .404 brass. If that .544 is correct, and I had a rifle and dies for an ultramag variant, rim diameter aside, would that .006 at the base make a difference if I tried to use .404 brass? Hope that was not too confusing.

One of my wildcats is a .358 X .404. This was made prior to the RUMs. I bought a bunch of RUM cases and could not size down the base diameters to fit my chamber. For the time, effort and money it would have cost me to moodify it I could suffer through using .404 cases. roger

Current .404jeff. brass is slightly smaller than RUM. I have used .375RUM brass to make .404 brass, just to see if I could. It requires alot of lube & patience but it can be done.
I'm not sure why you would want to make brass from a .404 case anyway. It's WAY more expensive than RUM brass.

quote:

Originally posted by fredj338:

"I'm not sure why you would want to make brass from a .404 case anyway. It's WAY more expensive than RUM brass."

Well in my case ,Fred,The .358X.404 preceded the Rum by a number of years. If I were doing it today it would be Rum De Dum all the way.

Fred, I understand the difficulties of trying to size down the RUM brass to fit a .404 chamber, what I talking about was using the smaller base .404 brass in a RUM chamber.

Well, my Norma 404 brass mic's about .542" at the base. If SAAMI minimum is .008" greater than the brass, then your chamber is somewhere around .558" around, maybe more depending on how used the reamer was on the day it made yours. That's potentially .016" out of round.
My chamber was cut to .548" IIRC, so the smallest RUM brass might make it into my chamber, but no room to expand.
Gixxer, why would you want to use 404 brass?

Well, its like this... You know what, scratch that idea. I was looking at different possibilities for a .458 cartridge based on the .404 because I was going to form brass from 404 basic brass(they are going for $33 for 20 from Mast). The reason for the inquiry about a RUM chamber is because most of the reamers that I have found are based off of the RUM case for the most part, and I did not want to spend the yak to have a reamer made. Also, I did not want to neck up 375 RUM brass because I do not want to test the limits of a thin neck from expanding so much. In the grand scheme of things I should just buy a bunch of 416 Rigby basic brass and go with the 470 Mbogo. The brass is the same price as the .404 basic stuff. You know, shame on big green for not resizing the .404 the way it was to make their RUM's.

The Mbogo is a great round, but I'm not sure you'll get a rifle chambered in it for any less than one in 458-404 (458 G&A, 458 Vincent Long, 458 Canadian Mag) after dies, reamer, etc.
I wouldn't base the decision on that, in other words.
Either a M70 in 300 RUM or a CZ in 416, resp, rebarreled will get you the rifle.

I forgot to mention that the whole idea around the 404 was because this idea was to be built on a push feed action, and I doubt the bolt face could be opened up to fit the Rigby rim diameter and still be safe. So, like I was saying, might as well spend the money for that super duper shiny Serengeti action, and go from there. Defeats the purpose of trying to save the money on the reamer, but then too maybe it is time for a CRF Mauser variant that is so much better than that Remington action that I was going to use. And to be honest with you, I think I would be happier with the Mbogo too.