Help me sort this one out please.

A buddy just called to ask me about the FN action that I intend to use for my custom. I told him I wanted to build a 338/284. He then very dryly says..."did you ever think about necking down a 350 rem mag?" Then he just chuckles because he knows I will obsess about this for a while.

Talk me down. Aside from horsepower/case capacity, what benefits would one have over the other?

I like your friends suggestion.
High quality .284 cases are available whereas .350RM cases are not.
I like the minimal size change from .358" to .338" compared to the much larger size change for the .284.
I prefer the belted case over the rebated case but most will disagree with that one I suppose.
Finally, I like the case capacity of the .350RM.

Like I said, your friend is a smart man.
And evil!

It's killin me, but I think the S.O.B. might be onto something.
It's kind of a horse apiece.

If I go with the .284 I have to have the ramp and rails VERY precise to feed out of the DBM.

I really like the idea of necking down 19/1000 as opposed to a multi-step necking up by more than twice that much.

But I eally don't like the belt, and I would have to open up the boltface to 13mm.

My goal was to propel a 180 gr. Bullet to exactly 3000 fps. and to be able to shoot between 180s and 225s consistently.

AAAAAAARGH!

Can the .284 case push a 180 to 3000?

The capacity twin to the 338-284 is the 338-06 and 3000fps is right at the outer limits of ability for it.

My source of load data for the 338-284 is loaddata and they have no loads shown at 180gr.

The .350RM case should be capable of holding 4-7 grains more powder so 3000fps may be more easily reached with it.

I'm still liking the 338-350RM

Since this is the Wildcats forum, I suppose I shouldn't mention the 338RCM.

No belt, and probably does what you want.

Darn good suggestion but I think the RCM just barely pushes 180's to 3000.
Ramshot lists 1 load going 3003.

284 all the way. Easy to find good quality cases, lots of data, and the 284 case is larger than the 350RM so you will be more likely to achieve your velocity goals.

Simply HAVE to ask this simple and obvious question.... If building from a Mauser action, why not the vastly superior 338 WinMag or another cartridge that will utilize your full Mauser bolt length? 338 Dakota, 338/375 Ruger etc. etc. Can't see building a funky short cased 338 in an action that can do more and better than that. Even a 338/06 would make more sense to me.

The 350RM case has GREATER capacity than the 284 case.

According to the "Handloader's Manual of Cartridge Conversion" the 284 has a capacity of 64.59 grains of water and the 350RM has a capacity of 73.74 grains of water.

The metric case capacities are 4.185CC's for the 284 and 4.770CC's for the 350RM

That is over a 9 grain difference in capacity in favor of the 350RM.

I'm not sure which action he's using except that it is made by FN and it has a detachable box magazine.
I guess I assumed it was a short action based on his cartridge choices.

INteresting, and I stand perhaps corrected. With such a fat unbelted case of a maximum length to work in a short action I would have bet folding money that the 284 case had a larger internal useful volume. Guessing it is still a touch behind that of the 338 WinMag which will fit just fine in a Mauser bolt action .....

I understand completely the idea of getting the most bang for your buck available when building on a short action of some kind but see no reason to handicap a wonderful 98 Mauser Actioned custom with a too short cartridge.

the 350RM is more than a little behind the 338WM
The 338WM holds 85.62 grains of water or 5.55CC's

The 350RM is bigger around everywhere you measure it than the 284.

If indeed he has a full length Mauser action then one of the LA cartridges makes a whole lot more sense.

the bigger question here is, the original poster owns a Swede.

why do you want to shoot anything else? sheesh.

As good as the Swede MAY be, it can't push a 180gr .338" diameter bullet to 3000fps.

To make life even more difficult! Have you thought about the .376 Steyr case????

8mmwapiti

The action is an FN PBR short action with DBM designed for 7.62 NATO. So alas, friends it must be a short action cartridge. Gratefully, the Steyr is too long for it.

I spoke to the gunsmith to ease my pains: The 350RM will not work with the DBM, but the .284 will. I could forgo the DBM, sell it and get Williams bottom metal that would feed the 350RM or I can stick with the .284. I like the DBM.

According to recent gossip, there are two guys at our range clocking 180gr NBTs at 2980 +/- 15 out of a 338-284. Close enough for me!

Matt...I have to have a .338 a voice in my head keeps telling me so. Then I will have covered the best calibers ever made:

.338 Illudium Space Modulator, .264(6.5 Swede), and .50 ML

whats wrong with the .338 Federal? its based on the .308 and is a .338 diameter that you want. brass and bullets are easy to find, and so are dies. only drawback i can see is that you can only shoot 180's to around 2800 fps, unless you get a minimum headspace chamber like i have. it shoots much faster for some reason, and wears out cases less as well.

I've got nothing against the 338 Federal. I actually like the idea of it quite a bit.
I just like the idea of having a cartridge that reaches the 3k mark with its lightest bullets and that extra 12% +/- of case capacity with the .284 will get me right up to it.

Oddly, I don't find many references to 338-06 pushing 180s out over 3k either.

The .338 Z-hat/Hawk is doing it on 58 gr of IMR 4320. With a shorter fatter powder column of IMR 4350 and just slightly less powder, I should maxing it out right in the neighborhood of 3k +/- 3% (If my math is good)

The 284 case has almost the exact same capacity as the -06 case so they run neck and neck to each other.
Did your 'smith say why the 350RM case wouldn't work in your DBM?

Yup. No deal with the DBM.

Go 33/284. Best possible format for the action and I like DBM's as well. 338 Fed is weak.....

Thanks to everyone.

I'm sticking with the .338-.284
The .350 with its fatter case and rim make box feeding a PITA according to the smith, and basically necessitate a blind mag or floorplate style bottom metal.

Doctorin' the feed rails is a lot simpler than losing the DBM, opening the boltface, and getting different but compatible bottom metal.

Dilemma resolved.