Designing My Last 7mm Cartridge

[Huntaddict]

I love wildcats and this one looks great!
My fav recently is on I call 7-300 PRC. Easy name, easy wildcat
Took the 300 PRC case and simply necked it to 7mm and did a custom freebore to handle up to the 195 Berger while using full case capacity and mag length. Runs the 180 Berger VLD at 3120
For comparison, here it is on the L next to a recent 338 NMI build I did.

 

[fseaman]

such as the 30-28 nosler.

That's me!
Nosler never said anything to me about it and I talked to their ballistician directly.

 

[fseaman]

@BoatTail

I love it. Well, I would as this is my favorite case family.

I see that you did extend the neck by 0.154 Allowing diameter seating depth. I believe this is an improvement over the 28 Nosler.

I did a model in QuickDesign and came up 11g H2O lower than the 28 Nosler. Nice!

My QuickLoad model with 180 Berger VLD seating .284 if shank is 2900-2950fps, 24 inch barrel. Again nice!

This should be a serious contender in LR BR and King of xxx type games.

 

[dogz]

Tons of Ballistic Gack being talked here

 

[vern.284]

Tons of Ballistic Gack being talked here

Lol I was thinking the same thing. Awesome project and following for sure...I built a 7saum over the wsm, always been a .284 fan
A switch barrel with this and a 404 Jeffery... perfection

 

[Mike Matteson]

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

You have put a lot of work into it.

 

[huntinfool18]

Wouldn't this be essentially a 7lrm?

 

[K.E.C. Darkside]

Wouldn't this be essentially a 7lrm?

What is a 7lrm?


The guy is having Fun, experimenting.
I like doing stuff like this myself, who cares if someone else did something like it. Merry Christmas.

 

[huntinfool18]

I'm all for wildcats, I have several. I'm not knocking him at all, it was a simple question.

 

[Rifleman97]

Wouldn't this be essentially a 7lrm?

Pretty similar, not exactly the same but similar goal for the round

Edit: OP's round is noticeably shorter overall, only slightly shorter to the start of the shoulder. 7lrm has more case capacity and also a longer neck, at least longer than the iteration in the first post. Not counting whatever is in the potentially later version as mentioned in one of the comments

 

[K.E.C. Darkside]

Pretty similar, not exactly the same but similar goal for the round

Edit: OP's round is noticeably shorter overall, only slightly shorter to the start of the shoulder. 7lrm has more case capacity and also a longer neck, at least longer than the iteration in the first post. Not counting whatever is in the potentially later version as mentioned in one of the comments

DELETE

 

[BoatTail]

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!

Here is the QuickDesign version of the Wildcat. I understand how to use it better than the Gordon's version:

 

[BoatTail]

In the Gordon Cartridge Design tool, when you click on the upper case S, the software highlights what looks like the 0.200" area from the end of the case. I used that in the design but it is showing red.

 

[john k]

Following.
Love this s...

Merry Christmas.

Me 2