.300 RUM brass necked-out to take .338 bullets = good stuff?


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Lucky
December 19, 2007, 04:53 PM
I'm looking at .338 rifles, and the costs associated with .338 lapua seemed quite large, and once I'd almost accepted them I learned that the Ackley-improved .338 lapua would be even better.

Then a gunsmith told me an alternative is to built a rifle around the .300 RUM cartridge, necked out to take the .338 bullets. He sounded great, said velocities would be same and still would use 300gr bullets in the 9.4 twist barrel, but at a fraction of the price for brass (and an action!).

Anyone done this, or heard about it?

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Jim Watson
December 19, 2007, 05:14 PM
Or you could just use the factory standard .338 RUM.

I confess I do not have the case dimensions at hand. Do you think he is saying a .338-.300 RUM would be better than a .338 RUM or is he just not aware of the factory round?

Lucky
December 19, 2007, 06:04 PM
Ohhhh maybe that's what he meant! Thanks. Maybe he meant they also had a die so people could neck out .300s to .338 and use 2nd-hand brass that way. Hydroforming he said.

Jim Watson
December 19, 2007, 06:44 PM
I have heard of hydroforming brass to wildcat calibers like the old Gibbs lineup and I want no part of it... or any wildcat, nor reforming of second hand brass to save having to buy the right stuff.

Lucky
December 19, 2007, 07:40 PM
I'm going in tomorrow to see them and will ask exactly that, if it's a standard .338RUM chamber or no.

Strongbad
December 19, 2007, 07:45 PM
The 338/300 is an improvement over the factory 338 RUM. The 300 RUM holds more powder. Remington made a bonehead move when they shortened the 338 RUM case and moved the shoulder back. It didn't take long for folks to figure it out and start chambering guns in 338/300. 338/300 should be a good choice for a Lapua alternative. Cheap brass and should be very accurate in a well built gun.

Jim Watson
December 19, 2007, 07:53 PM
Ah-HA!
So it IS bigger. Thanx, Strongbad.
How many fps do you buy with the wildcat?

Lucky
December 19, 2007, 08:16 PM
Yes thanks Strongbad, I guess that case wanted to be more awesome!

Strongbad
December 19, 2007, 10:19 PM
No sweat. The name given to the 338/300 RUM btw is the 338 Edge. From the data I've been able to dig up and judging by the case capacity, the Edge is everything that the Lapua is and possibly more. Longrangehunting.com will have a lot more info, do a search over there and you'll find more info about it than you care to read.

MachIVshooter
December 20, 2007, 12:28 AM
The 338/300 is an improvement over the factory 338 RUM. The 300 RUM holds more powder. Remington made a bonehead move when they shortened the 338 RUM case and moved the shoulder back. It didn't take long for folks to figure it out and start chambering guns in 338/300. 338/300 should be a good choice for a Lapua alternative. Cheap brass and should be very accurate in a well built gun.

The performance increase is there, but it's fairly negligable. For most, the extra 100 FPS isn't worth having to wildcat. The factory .338 RUM is still quite a sledgehammer, with ballistics basically equal to the .338 Lapua.

Oscar1
October 30, 2008, 06:03 PM
Another name for it is the .338 ultra cat. I'm re-enlisting soon and building one for long range elk. This site has reloading dies as well. http://www.z-hat.com/Ultracat.htm

Strongbad
October 30, 2008, 06:08 PM
As it turns out, I have a friend who had a 338 Edge built a while back (earlier this year). After shooting the snot out of it, his conclusion was that it wasn't worth the hassle of a special chambering, necking up the brass etc. He said that if he did it again he'd just go with a 338 RUM and be done with it.

telecaster1981
October 31, 2008, 12:44 AM
Not meaning to hijack here...perhaps my question will lend to the OP's intended discussion.

I've been running numbers on ballistics programs the last few days trying to figure out what makes the .338 Lapua a superior round to the .300 RUM. As far as I can tell, when the .300 RUM is pushing something like a 210-240gr Sierra Match King at around 2900-3000fps, it appears to actually surpass the .338 Lapua ballistically Anyone else looked into this?

MTMilitiaman
October 31, 2008, 01:48 AM
The 338/300 is an improvement over the factory 338 RUM. The 300 RUM holds more powder. Remington made a bonehead move when they shortened the 338 RUM case and moved the shoulder back. It didn't take long for folks to figure it out and start chambering guns in 338/300. 338/300 should be a good choice for a Lapua alternative. Cheap brass and should be very accurate in a well built gun.

Actually, my understanding was that this was done as safety measure to prevent .300 RUM being chambered in .338 RUM rifles.

The .338 RUM is capable of some very good performance in its own right. My dad has a custom .338 RUM built around a M700 action with a 30 in Lilja #5 stainless fluted barrel in a McMillan sporter stock. From the 30 inch barrel, he is getting over 3100 fps from 250 gr Matchkings pretty easily. I don't have a lot of experience with it, but I know I've done some shooting out to about 800 yards with it and the impact at those distances comes right at the shot. Those rounds don't waste any time at all getting down range and on slat rocks, the impact sounds, shall we say, authoritative.

As for the .300 RUM vs. .338 Lapua, I couldn't say. I don't have my external ballistics software here. But I doubt it. Esp if you look into the 300 gr Matchkings for the .338--I think to do any better you're probably going to have to go to the exotic proprietary .40+ caliber cartridges and the .50 BMG.

mickman
November 1, 2008, 04:50 AM
aside from numbers bragging, what is the difference in 100 +/- FPS or ftlb's of energy at xxx distance? :scrutiny:
if you are shooting at a distance that the extra energy is absolutely neccessary, then it's probably too far away..

SimpleIsGood229
November 1, 2008, 03:36 PM
While you're handloading, take a look at the .338-378 Weatherby Magnum.

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