Is the 450 Rigby the same cartridge as the 416 Rigby but necked up to .458? Could one take a CZ550 in 416 Rigby and rebarrel to .458 with no other modifications?

almost, yes!

Also called the 450 Dakota in one variation.

Close, the parent case for the 450 Rigby is the 416 Rigby. The parent for the 450 Dakota is also the 416 Rigby. 450 Rigby and 450 Dakota are nearly the same case size, but not interchangable.

I am rechambering a 458 Win, a new CZ550 rifle, to 450 Dakota for a customer. The Dakota has the edge on the Rigby in ease of obtaining brass, but it is still expensive at $2.25 each from Dakota.

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John,

What exactly is the difference? The only 450 Rigby I ever saw was in fact nothing more than a 416 Rigby necked up to .458. This left the shoulder diameter at .540". The Dakota, which I have never measured is advertised to have a shoulder diameter of .560" same as the 460 Weatherby. In actuality the 450 Dakota is nothing more or less than a beltless Weatherby with a traditional single angle shoulder.

Just curious.

Todd E

The shoulder angle on the Rigby is slightly sharper than that of the Dakota. I'm not sure which one is the "better" design. In factory ammunition, the Dakota is loaded hotter than the Rigby but I load mine cooler than either. I suspect that one could shoot either one alternately for a lifetime and never notice any difference.

Sarge

Sarge,

What is the shoulder diameter of your 450 Rigby?

Todd E

I can't remember. Is the 416 Rigby shoulder angle 35 or 45 degrees? I know it was pretty darn sharp for a cartridge from that era.

Is it different on the 450 Rigby?

-Catter

Catter,

The 416 Rigby has a 45 degree shoulder angle. Sarge can tell us what the 450 Rigby shoulder angle is.

Todd E

I interviewed Art Alphin about the designs he did for the Dakota line of cartridges. Art said that he based the .450 Dakota on his A-Square Excalibur case.

Measuring cases I have yields the following shoulder dimensions:

.450 Dakota .552"
.450 Rigby .563"
.460 Weatherby .559"

The Dakota looks to have a less sharp shoulder angle than the Rigby (looks the same as the 45 degree .416 Rigby), and the Weatherby looks like a venturi shoulder but similar to the Dakota.

David Lyttle of KYNAMCO told me you need to start with proper .450 Rigby brass, necking up a .416 Rigby case gets you close but not exact.

jim dodd

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hunt, you are too busy."

Here are the numbers from my reamer drawings, reamers were made by Dave Kiff of Paciffic Tool:

450 Dakota:
26 degree shoulder
Shoulder diameter is 0.562"
Shoulder is 2.326" from the bolt face
Chamber length, bolt face to end of neck, is 2.910"

450 Rigby:
Shoulder angle is 33 degrees 45 minutes
Shoulder diameter is 0.5728"
Shoulder is 2.344" from the bolt face
Chamber length, bolt face to end of neck, is 2.906"

416 Rigby:
Shoulder angle is 44 degrees 45 minutes 30 seconds. For all practical purposes this is 45 degrees.
Shoulder diameter is 0.5409"
Shoulder is 2.3512" from bolt face
Chamber length, bolt face to end of neck, is 2.912"

Keep in mind that new unfired cartridge cases will have smaller dimensions than the chambers, especially at the shoulder diameter. Also, reamer, and chamber, dimensions vary from manufacturer to manufacturer. And, as reamers wear and are reground, the dimensions change a bit, even at the same gun builder. The reamers I mentioned above are ground to SAAMI (American) or CIP (European)specs.

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Currently in Exile on the Beautiful Olympic Peninsula of Washington State.

My Warden sometimes allows me to respond to email. NEW Address is rifles@earthlink.net

***********Jail Flash*******
Web site under construction: http://home.earthlink.net/~rifles/

[This message has been edited by John Ricks (edited 03-09-2002).]

[QUOTE]Originally posted by John
If your interested there is a picture of the 416 Rigby and the 450 Rigby along with a 470 Mbogo (based on the 416 Rigby case) sitting side by side on my website. Just click on the picture and it will enlarge. A picture is worth a thousand words. They are all big.
www.470mbogo.com

470 Mbogo

Todd,
.568 on unfired cases, .573 on the fired ones.
Sarge