Designing My Last 7mm Cartridge

Over the last 15 years I have fallen in love with the cartridges in the 7mm family. Working with, and modified multiple 7s including the 7mm RUM, 7mm Rem Mag, 7mm – 08, 7mm WSM, 7mm LRM, and the 28 Nosler, each has taught me something new as I struggled to find the optimum neck size, freebore and load for best accuracy and performance. I found that each had some value or purpose, except maybe the 7mm RUM that, without a muzzle brake, seemed to violate every part of me when I pulled the trigger.

With the end of my physical ability to hunt, I will be switching over to benchrest competition to feed my need for reloading, testing loads, bullets, powder, and shooting sports. Before do so, I wanted to build one more long-range hunting rifle. This one will be used occasionally, while taking advantage of handicap mobility privileges, for Antelope hunting. The rifle will be a 7mm wildcat that provides more than the 7mm Remington mag, 7mm PRC and 7mm WSM, but less than the 7mm RUM and 28 Nosler.

Care to guess what is? I have dubbed it temporarily as the 7mm Nosler Short Mag (NSM). Here is how it compares visually to some of the other 7mm 404 Jeffery based cases that I have worked with:


Basically, the 7mm NSM is the 28 Nosler case shortened to 2.35". It retains the neck length and shoulder angle of the 28 Nosler. The new case is close to the 7mm Blaser Mag developed in Sweden. Like the Nosler and Ultra Mag cartridges, the 7mm Blaser Mag cartridge is based on the 404 Jefferies case. The primary difference between the 7mm Blaser Magnum and 7mm Nosler Short Magnum's Body Taper and Shoulder angle. The angle on the Blaser is 30 degrees while the 7mm Nosler Short Magnum is 35 degrees. This 7mm NSM case also uses the neck diameter and Freebore of the 7mm PRC. This altered case has about 4-5 more grains of H2O compared to the 7mm Blaser Mag.

My challenge now is to validate third party load data for the 7mm Blaser Mag or to show the 7mm NSM can meet or exceed them. The Chamber drawing in QuickDesign seems to be right, but I need help with the Gordon Cartridge Designer. I have attached the Gordon drawing and data fore review.

Note on the Gordon Chamber drawing the "S" Dimension has a problem. I assumed incorrectly what is was. Can someone help me with it?
I thought it was the dimension from the base of the case to the base or start of the body. Thoughts?

just when i thought the "nsm" was Not So Much

i've been trying to get a complete rendering in quick design, but no luck so far. good luck!

One thing I would consider, would be to increase the neck length since you have so much extra brass to work with. It could potentially gain you some capacity depending on the bullet you plan to shoot and the throat length you plan to use. It would also ensure that you could stay away from any donut that may form at the neck/shoulder junction.

Once you finish let me know how to get a reamer and brass. I have been saying since the 7mm PRC came out that it should have looked like what you have here. The PRC left meat on the bone by not using the 404 Jeffrey case. I love this cartridge. I have a feeling winchester/browning is already working on this though. Great job!

Following

Maybe reach out to Ray Gross at Manson Reamers for some help and then you've got a in with a reamer maker! He's helping me now with a 25 Creedmoor reamer and some
minor changes.

Following - designing a wildcat has always been an interest! love the details provided and work. wish i could help.

BoatTail said:

Over the last 15 years I have fallen in love with the cartridges in the 7mm family. Working with, and modified multiple 7s including the 7mm RUM, 7mm Rem Mag, 7mm – 08, 7mm WSM, 7mm LRM, and the 28 Nosler, each has taught me something new as I struggled to find the optimum neck size, freebore and load for best accuracy and performance. I found that each had some value or purpose, except maybe the 7mm RUM that, without a muzzle brake, seemed to violate every part of me when I pulled the trigger.

With the end of my physical ability to hunt, I will be switching over to benchrest competition to feed my need for reloading, testing loads, bullets, powder, and shooting sports. Before do so, I wanted to build one more long-range hunting rifle. This one will be used occasionally, while taking advantage of handicap mobility privileges, for Antelope hunting. The rifle will be a 7mm wildcat that provides more than the 7mm Remington mag, 7mm PRC and 7mm WSM, but less than the 7mm RUM and 28 Nosler.

Care to guess what is? I have dubbed it temporarily as the 7mm Nosler Short Mag (NSM). Here is how it compares visually to some of the other 7mm 404 Jeffery based cases that I have worked with:

View attachment 626650
Basically, the 7mm NSM is the 28 Nosler case shortened to 2.35". It retains the neck length and shoulder angle of the 28 Nosler. The new case is close to the 7mm Blaser Mag developed in Sweden. Like the Nosler and Ultra Mag cartridges, the 7mm Blaser Mag cartridge is based on the 404 Jefferies case. The primary difference between the 7mm Blaser Magnum and 7mm Nosler Short Magnum's Body Taper and Shoulder angle. The angle on the Blaser is 30 degrees while the 7mm Nosler Short Magnum is 35 degrees. This 7mm NSM case also uses the neck diameter and Freebore of the 7mm PRC. This altered case has about 4-5 more grains of H2O compared to the 7mm Blaser Mag.

My challenge now is to validate third party load data for the 7mm Blaser Mag or to show the 7mm NSM can meet or exceed them. The Chamber drawing in QuickDesign seems to be right, but I need help with the Gordon Cartridge Designer. I have attached the Gordon drawing and data fore review.

Note on the Gordon Chamber drawing the "S" Dimension has a problem. I assumed incorrectly what is was. Can someone help me with it?
I thought it was the dimension from the base of the case to the base or start of the body. Thoughts?

View attachment 626651
View attachment 626652

Click to expand...

following

Can you use Nosler's name? I thought it would trademarked

Thanks

Buck

Bucklowery said:

Can you use Nosler's name? I thought it would trademarked

Thanks

Buck

Click to expand...

It's the same thing as any other wildcat, such as the 30-28 nosler. It's not meant to be used as that brands design, but simply indicating it uses them as a parent case. As long as you don't intend to make money with the name you're good. And even if you do, if the amount you make is low enough and the name doesn't hurt their reputation in any way they'll have no reason to go after you for it. Before the final release I would come up with a more unique name though. Like 7mm insert designer last name here. 7mm Sherman comes to mind as it's a wildcat (series of wildcats really) with a very simple name. Then you can make larger or smaller versions of it and keep the name rather than being 33-28 nosler short mag, it would be just 33 Lastname

Awesome

BoatTail said:

Note on the Gordon Chamber drawing the "S" Dimension has a problem. I assumed incorrectly what is was. Can someone help me with it?
I thought it was the dimension from the base of the case to the base or start of the body. Thoughts?

Click to expand...

The S dimension on the chamber is just a reference distance from the breech at which you can specify a diameter. For example the SAAMI chamber drawing for 28 Nosler specifies 0.5533" at the breech, and 0.5510" at the reference distance 0.200" forward of the breech.

See page 87 at this link. https://saami.org/wp-content/upload...99.4-CFR-Approved-2015-12-14-Posting-Copy.pdf

Sounds like a fun project, can't wait to see how it runs


Thanks

Buck

Following. I love wildcats!!! Looking to build 30 or 7mm cal next. This may be it.