what is this 7mm called ?

Daveinjax

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I've been thinking about what I want in a standard long action 7mm and have come to a rough idea. I'm sure I'm not the first so I'm trying to find someone else's project and experiences so I don't have to blow a bunch of cash out for no reason. I'm thinking of a 404 nitro case blowed out to minimum taper , shoulder bumped back to about 1.92 " , 32.5º shoulder angle , and a 2.5" total case lenght. The 7mm LRM is close but no cigar. How hard to form ? Is it basically already made ?
 

MudRunner2005

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.404 Rimless Nitro Express is based off of the .404 Jeffery case, which is what the RUM calibers are based off of.

But not familiar with any of the variations set at 2.5" case length...
 

MudRunner2005

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It would basically be a fatter, beltless version of a 7mm RemMag with about 16 more grains of water capacity, and a sharper neck. But it is longer than the WSM & SAUM calibers.

I just drew it out on my software, and compared it to a 7mmRM if you would like me to, I can post it up on here for you.

It is pretty interesting looking, though...I kinda like it.
 

MontanaRifleman

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You are describing something very similar to a 7 Dakota. The Dakota shoulder is 1.98 with an angle of 30*. Case OAL is 2.500. Neck is .330.

What you're describing would have something like a .390 neck.

I'm not familiar with the 404 nitro case, but if it's anything like the 404 jeff, i think you would be in for a lot of work trying to form what you are describing. It would be much easier using the 7 Dakota case, but shortening shoulders is no easy or simple task.
 

7mmRHB

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Sounds like the 284 STAK which is a 300 Dakota ( a true 404 Jeffries case ), at 2.555, necked to 7mm and improved ( 40* w/ .012 taper )

The STAK will push the 180s over 3200fp

The 7mmRHB is a shortened RUM case, 2.555, 35* shoulder, .015 total taper. It holds 4 more grains of powder than the STAK. This case is hard to make so just stick with the Dakota brass.

The 7mm Dakota case is significantly smaller in case capacity than the 300 Dakota. --- RHB
 

Daveinjax

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My thoughts are enough powder to push the long promised 195 gr berger to 3100 fps with the bullet above the neck / shoulder junction and not quite as thick as a necked down 338 norma. Norma makes the 404 Jeffries brass and it's shoulder is at 2.0 " . My problem with the 338 norma is that it's at the maximum of what a standard Remington action can handle for both diameter and length and really is too much powder. I'll have to look at the Dakota case. Working right now so...
 

MontanaRifleman

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Sounds like the 284 STAK which is a 300 Dakota ( a true 404 Jeffries case ), at 2.555, necked to 7mm and improved ( 40* w/ .012 taper )

The STAK will push the 180s over 3200fp

The 7mmRHB is a shortened RUM case, 2.555, 35* shoulder, .015 total taper. It holds 4 more grains of powder than the STAK. This case is hard to make so just stick with the Dakota brass.

The 7mm Dakota case is significantly smaller in case capacity than the 300 Dakota. --- RHB

It depends on your definition of "significantly smaller" The 300 Dakota is .106" longer at the shoulder than the 7 Dakota. I'm guessing that amounts to about 4 gr of powder, or 5% capacity difference.
 

MudRunner2005

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You are describing something very similar to a 7 Dakota. The Dakota shoulder is 1.98 with an angle of 30*. Case OAL is 2.500. Neck is .330.

What you're describing would have something like a .390 neck.

I'm not familiar with the 404 nitro case, but if it's anything like the 404 jeff, i think you would be in for a lot of work trying to form what you are describing. It would be much easier using the 7 Dakota case, but shortening shoulders is no easy or simple task.
The neck on my diagram that I drew up for his cartridge is .249"...

It also has a .0100" taper, so it should have close to a 100-105gr water capacity.

It does sound very close to the Dakota, but I don't have any of the Dakota calibers on my software to compare it to.
 

MontanaRifleman

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My thoughts are enough powder to push the long promised 195 gr berger to 3100 fps with the bullet above the neck / shoulder junction and not quite as thick as a necked down 338 norma. Norma makes the 404 Jeffries brass and it's shoulder is at 2.0 " . My problem with the 338 norma is that it's at the maximum of what a standard Remington action can handle for both diameter and length and really is too much powder. I'll have to look at the Dakota case. Working right now so...

Pushing the 195's to 3100 fps will be a tall order. I don't think it's gonna happen in a Dakota case. Probably very doable in a 7 RUM or 7 Lapua with RL33.

I would not build a Lapua or NM cartridge on a 700 action. IMO, the bolt thrust of those cartridges is pushing the 700 near its max. It's been done... I just wouldn't do it.

A 700 action with a Wyatts extended box will easily fit the 7 RUM
 

MudRunner2005

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Pushing the 195's to 3100 fps will be a tall order. I don't think it's gonna happen in a Dakota case. Probably very doable in a 7 RUM or 7 Lapua with RL33.

I would not build a Lapua or NM cartridge on a 700 action. IMO, the bolt thrust of those cartridges is pushing the 700 near its max. It's been done... I just wouldn't do it.

A 700 action with a Wyatts extended box will easily fit the 7 RUM
Yep, that Wyatt's extended mag box is 4.000". That's a LONG cartridge. I would easily be able to seat my STW rounds and use it as a repeater. Which I will probably do when I build my .300 Ackley.
 

MagnumManiac

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I've been thinking about what I want in a standard long action 7mm and have come to a rough idea. I'm sure I'm not the first so I'm trying to find someone else's project and experiences so I don't have to blow a bunch of cash out for no reason. I'm thinking of a 404 nitro case blowed out to minimum taper , shoulder bumped back to about 1.92 " , 32.5º shoulder angle , and a 2.5" total case lenght. The 7mm LRM is close but no cigar. How hard to form ? Is it basically already made ?

Sounds like a 7 Dakota to me?

Cheers.
gun)
 

Daveinjax

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I just got time to look at the 7mm Dakota and it looks like what I might want. I'm going to a gun show in the morning and if I see the right donor action at the right price this project might get started.
 

7mmRHB

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The 300 Dakota case holds at least 7grs more powder to the shoulder neck junction than the 7 Dakota. That seems fairly significant !! The 7 Dakota will be lucky to get 3050 w/ 180s let alone the 195s. The 284 STAK or 7mm 300 Dakota IMP will probably get 3000 plus fps w/ the 195s if there ever is a 195.

Berger was telling folks at the SHOT show, that they were going to change everything to the Hybrid shape and have a hunting and target version only. That will push the 195s further on to the back burner!!--- RHB
 
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