300 RUM from New 7mm RUM Nosler Brass

[Double Dropper]

Like the title says I scored a 100 rounds of new 7 mm Ultra Mag Brass. Can I neck size up the brass Can I neck size up the brass Into the larger caliber and Everything work properly ? 300 RUM brass is very hard to find and this brass is brand new

 

[dustbag]

JA Outdoors had ADG 300 rum in stock

300 RUM -

300 Rum Brass, All ADG Brass is offered in a 50-piece retail box that utilizes a custom ammo box and foam liner to protect the brass during shipment.

jaoutdoors.com

 

[Double Dropper]

Not helpful, I am in Canada , does that appear to answer my question?

 

[dustbag]

Sorry didn't know about Canada.

 

[Double Dropper]

I am well aware that I could probably try to source some brass from the United States and get it shipped up to Canada But I already have a 100 rounds of expensive brass

 

[Hand Skills]

Hello Beaver Country! Originally Yellowhead County myself.

Yes, the 7mm RUM and 300 RUM share the same headspace - you 'could' just run the necks through a mandrel and load, but I can't recommend it.

You could sell the NOSLER brass and buy some ADG 300 RUM

ONLINE STORE - Go Big Tactical - gobigtactical.ca

Go Big Tactical is a Firearms, Optics, and related asscessories business based out of British Columbia Canada

gobigtactical.ca

In stock, and some of the best brass available for the 300 RUM.

Either way, stay safe and happy shooting!

 

[Shane Lindsey]

Curiouos myself. I am thinking no because the 7 is longer in the shoulder by .019". Not sure you could bush it back enough to start.

Hopefully someone has done it or has tried and can recommend.

@Elk Hunter 338

 

[Dean2]

Try chambering the 7 RUM brass in your rifle, my bet is it will fit no problem. Even if the new brass is long enough in the shoulder to not chamber, sizing it will solve that problem. Adjust your FL die a bit at a time till the case will just chamber, do this step without the expander button in place. Once you have the neck shoulder junction right put the expander ball back in. Run it through your 300 Rum FL sizing die, re-test chamber fit, then load and shoot it. It will work just fine. You can move rbrass a long ways and do no harm. I size 460 Bee brass down to 338-378. That 460 brass was originally made from 378 brass necked up to 460, but since I don't have a 460 anymore figured I would neck it back down to feed the 338-378 I just had built. That is way more brass movement than necking up from .284 to .306. Just make sure you lube inside the necks along with the outside of the case when you run the expander ball in.

460 to 338-378

 

[Frank in the Laurels]

...it will work, lots of lube and slowly push the ram as in REAL SLOWLY...the biggest problem will be it's marked 7mm rum, loaded with .308 bullets..make sure you have the cartridge carrier marked .300 rum CLEARLY..something happens to you and someone else gets a hold of them and loads .30 cal in .28 bore..LOOK OUT !! ...I know a person who uploaded .270 brass to 30/06 and that happened to the new owner, the results were not pretty !!!

 

[tim_w]

Always a very good idea to mark/document cases you alter from the case headstamp. In this case even with loose min and max tolereance stacking it will not fit.

But that 270 to 3006 is a unpleasant surprise as the headspace difference is almost perfect for the 3006 case mouth to jam fit a 270 chamber neck to push that case base firmly against the bolt face. Ooch


Still always a good warning to consider.

 

[Elk Hunter 338]

Hell yeah !! neck er up and let er eat! done it a bunch and vise versa

your mandrel in you 300 rum die will work fine !! dependent upon dies being used of course

I like the 308 tapered mandrel from redding or the hornady mandrel is tapered also

its a simple necking up from .284 to .308 easy peasy

i always use some imperial wax on the inside just to help things out ... be sure too clean all of it out before loading

 

[Double Dropper]

Well, for the folks who chimed in with , yes it can be done, thank you. For the Captain Obvious crowd, Like I had no idea the base of the brass would say 7mm RUM, thank you so much for that, I would have never known. I have been reloading for 35 years and asked a simple question. No one would somehow get ahold of my hand loads or my spent brass, even if they got the 7mm brass, and planned to use it....they would neck it down again. I have never lent, borrowed or shared my custom hand loads ever! It is already necked up and being fine tuned for length for the first firings. Thanks to all.

 

[Lefty7mmstw]

yup... 1/2 my 300rum brass says 7rum and some of my 7rum brass said 300rum for my last barrel. This barrel is using all 7rum brass as the chamber is rather tight. I'm skim turning the brass too for this barrel.

as far as the mis-marked brass... they won't cross chamber unless something is grossly wrong. .024" inch is a a decent amount of difference

 

[jasonco]

Short answer: Yes.

But use a tapered expander.