I am considering a .300RUM for LR shooting, maybe next year.

Just much does forming the brass from .404 cases entail and how much better would the quality and uniformity be than .300RUM Remington brass?

Aussie, pard;

I see from your address (Italy) that you may have a different set of problems than we have in the USA.

However, my "case" is just the reverse of yours: I make my .404s from .338 or .375 Remington Ultra Mag brass. Rather than spend two dollars per case for .404s, I find that the $12.00-per-20 UMs make excellent .404s.

Have you had bad experiences with the Remington brass, or is it simply that you can get .404s cheaper than we can? Or, is the .404 brass more easily available than the Remington cases?

If you do go this route, close attention should be paid to the neck thickness of the necked-down cases. Other than that, I see no problems. Generally, brand-new brass will give better results than once-fired cases when case-forming.

Regards from BruceB (aka Bren Mk1)

Further to my above answer, it is possible that an intermediate sizing die MIGHT be needed to do this job. In that case, I'd probably buy a standard .338 Ultra Mag sizing die, which will be a whole lot cheaper than a custom-made one. If you wish to do the sizing-down in smaller steps, then get a .375 UM sizer as well.

However, if you do the sizing-down in small increments, and lightly re-lube the cases between trips through the die, it may just work with only the normal .300 UM loading dies. Note that the SEATING die is larger in its inside dimensions than the re-sizing die, and thus may offer a sizing step just a bit less extreme than the actual .300 re-sizing die.

Regards from BruceB (aka Bren MK1)

I'll bet you'll have a hard time finding Remington brass that's as uniform as Horneber or Norma, if that's who you're talking about.
After necking, you'll need to turn the outside to get the right neck wall thickness.

Also, realize that you're likely working with a base diameter difference of .01" between your chamber and 404 brass. That's pretty sloppy.
Most 404's seem to run around .541" at the base, and I believe the RUM chamber is somewhere right at .551".... Remington brass if you can get it will measure about .546" or so.
May very well affect accuracy, which at long range is most of what you're worried about.
Going the other way like Bren Mk1 is doing will give you a tight chamber, since those are only cut at .546" to begin with.

EXPRESS,

We do this all the time, forming 404 brass all the way down to 375, 338, 300 and 270.

We have a custom made forming die from Neil Jones, It has bushings of varying sizes.

I found I have to go through 4 step downs at least to form 300 caliber brass if I did not wish to loose at least some cases because of collapsing shoulders.

Gents;

The actual base dimensions of cases here before me, miked immediately in front of the extractor groove, average of five cases per measurement, are:

Kynoch Berdan-primed .404 Jeffery: .541-.542"

Kynoch Boxer-primed .404 Jeffery: .544-.545"

Remington .338 Ultra Mag: .545"

NONE of these give even the faintest hint of "tightness" in my British-made rifle, and it's obvious that the dimensions are a very close match indeed.

As to the relative quality of the brass from different manufacturers, I can't say. I do know, however, that the Remington cases work perfectly for my .404 shooting, and they measure and weigh very consistently when such things are checked.

The demands that might be placed on a .300 UM for longer-range work are rather different than those met by a .404, and perhaps some handloaders may be fussier than others in such instances. I know that using this Remington .338 Ultra brass wouldn't lose me any sleep!

The next batch I re-form to .404 will be based on the .375 UM case, because it's slightly longer than the .338 UM case for some reason.

Regards from BruceB (aka Bren Mk1)

Bruce, I'll be interested in hearing about your experiences with the 404-375 RUM cases.
How hot do you load the 404? Do you full-length resize? Do the caseheads expand at all?
According to the drawings I've seen, you have about .001" clear at the base of the Boxer-primed, which if not loaded to high, should stay right there.
I have a chamber being cut for Norma brass, at .545-6" at the base, and I won't be able to resist trying out some RUM's as well.

EXPRESS, pard;

I tried to answer your post last night, but I reckon my post disappeared in cyberspace.

I bought my .404 over thirty years back to use on Woods Bison in the Northwest Territories. We residents could hunt them each year just by buying a $25.00 tag, and we went buff hunting every chance we could.

The only .404 bullets that were readily available were the 400-grain Barnes Originals, the copper-tubing-jacketed design. With the .049"-thick jackets (not the thinner .032" type) these performed very well on Woods Bison, which commonly weigh well over a ton for big bulls. Using Norma 204 or IMR 4350, my loads were just a bit over 2400 fps from my rifle's 21" barrel, or the full equal of a .416 Rigby factory load....not a bad ballpark! This was a gain of almost 300 feet per second over the 400-grain factory load. The recoil was noticeably increased too, let me assure you! I actually had a chronograph even 'way back then in the early '70s; one of the break-the-two-screens, turn-the-switch, add-the-numbers, refer-to-the-tables types....but it worked, and the info was always fascinating.

My main interest in higher-speed .404 loads was to flatten the trajectory as much as possible, because the ranges involved went from twenty FEET to over 200 yards in my personal experience. The .404 has a very gentle shoulder angle, and minimal sizing is the best way to avoid early head separations in such a design. It feeds slicker'n cow slobbers, though.....

In the 300 Ultra, I'd use once-fired brass from YOUR OWN rifle for hunting loads, and size it until easy chambering is absolutely certain. If this means sizing until the shellholder bumps the die, so be it. The case design has a sharp and prominent shoulder for good headspace control.

Your chosen chamber dimensions seem to be a good pick. All the brass types I have here would fit your chamber just fine, and it sounds like the Norma stuff will too. A few thousandths is really pretty meaningless at the cartridge base, as long as the round will chamber freely. A bit undersize does no harm either, witness those Berdan cases of mine at .541".

My cases do not seem to expand at the base to any degree, but I must admit that ALL my loads in the .338 Remington Ultra cases were with cast bullets. This does NOT mean that they were necessarily low in pressure, because some of them are very snappy indeed. "Cast bullet" is NOT synonymous with "low pressure". My .416 Rigby, for example, can drive a 365-grain cast bullet to over 2600 fps with fine accuracy and no leading whatever.

For some reason which escapes me, Remington made the .375 UM case a tad longer than the .338 UM, meaning the .375 is actually full .404 length and the .338 is a trifle short. No .375s were available at Midway when I ordered, so I decided to try the .338s anyway. They work fine.

Keep us posted on what you decide and how it works out, please.

Regards from BruceB (aka Bren Mk1)

Bren MkI - actually it's the other way around. The 300 and 375 RUM were designed to be full length, and the 338 RUM was designed to be shorter. I understand it was delibrate to fit the 338 RUM OAL into the Remington's action 3.6" magazine box with the available .338" bullets designed for the 338 Win Mag. Apparently some of the 338 bullets use a cannalure that Remington wanted to position correctly for the 3.6" OAL of the cartridge.

CMc, pard;

Yep, that makes perfect sense, and after I'd posted I realized that I'd gotten the cart before the horse.

Obviously, the .338 UM is the odd-man-out in the series, with the .300 and .375 being the "proper" length. Your explanation explains the reasons nicely, too.

When loading cast bullets, it is desireable to NOT have that gap between the end of the case and the end of the chamber, because the softer material of the cast bullet's base can actually bump up in diameter in that short space, and then have to be swaged back down again in the throat....not a good state of affairs.

My initial "go" at this reforming was intended to merely find out if it is practical, and it is eminently so. Future refoming will be done with .375 cases, and these have the added feature that much less neck expansion is needed, thus reducing the stree on the brass.

Thanks for chiming in!

Regards from BruceB (aka Bren M1)

Express, It's been a while since you posted. If you are still interested:
I have two wild cats for which I use .404 Bell and Norma brass and also.375 Ultra mag. brass. One rifle is in .358 and the other is an 8m/m. I have had little or no problem fire forming either.

Dont waste your time trying to form Norma 404 brass to 300 RUM,use the remington brass,it is adequate. I know this because I did the same thing for my 375 ultra,it was a royal pain! I did not see any real benefit to accuracy by using the reformed norma brass,oh yeah you will also have to turn the rim toget it to fit the boltface.My 2 pennies.

Here's a question for you guys loading the jeffery with rum brass. Do you have any extracting or feeding problems considering the rum brass has a smaller diameter rim than the jeffery brass? Would you still trust it on dangerous game?

First, I've had no functioning troubles at all with Ultra Mag brass in my Mauser '98-based .404. I think I've fired about 200 rounds in UM brass to date.

All my Kynoch brass has been fired several times, so could have tiny burrs etc, but the Berdan-primed Kynoch cases measure .537-.538" on the rim, and the Boxer-primed Kynochs run .539-.540". Once-fired Remington .338 UMs vary a bit from .533 to .537", and unfired .375 Ultra Mags are a consistent .532-.533".

We're only looking at a spread of about .007", and this isn't enough to give feeding troubles in my opinion and experience. What the UM brass DOES help with, is that it fits a standard H&H-size shellholder perfectly, where .404 brass is often (but not always) a tighter fit.

I just loaded up 40 rounds of .375 UMs for fire-forming tomorrow morning. First, the cases are sized just enough to chamber in the rifle, with the decapping stem removed from the sizer die. This sizing takes hardly any effort at all. I then use a smallish charge of fairly fast-burning powder under a caseful of Cream 0f Wheat, with a small tuft of dacron or piece of tissue loosely installed in the casemouth to keep the stuff in. NO BULLET! Firing straight up in the air gives nicely-expanded necks and final forming of the whole case.

Regards from BruceB (aka Bren Mk1)