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Designing My Last 7mm Cartridge

After building rifles in 7 Rem Mag, 7 Wby, 7 STW and 7WSM; I concluded that the 7WSM was the perfectly balanced .284 cartridge. Apparently, the shooting public disagreed. Now I'm shooting a 7PRC like everyone else. :D
The WSM is still being chambered though in factory rifles. Also Hornady just released Factory ammo offerings in the Precision and Outfitter lines! I think one is the 150CX and the other the 162ELDX.
 
I would do a .300 length neck at a minimum. I played with one wild cat with a .400 length neck, and this long neck reduced throat erosion tremdously in a 6mm case with 105s screaming.

Not many true experimenters out there.

7mm Mashburn Super is a really great cartridge, what the 7 Rem mag should have been, which has a .300 long neck.
 
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To the question of what is the dimension "S", is that the point where the bullet diameter starts getting smaller?
 
I would do a .300 length neck at a minimum. I played with one wild cat with a .400 length neck, and this long neck reduced throat erosion tremdously in a 6mm case with 105s screaming.

Not many true experimenters out there.

7mm Mashburn Super is a really great cartridge, what the 7 Rem mag should have been, which has a long neck.
Spot on Vince, I've been using the Mashburn Super for 3 decades, IMO one can't find a better balanced Big 7. Plus how cool is it that this round came out 65 years or so ago and people are still trying to better it...........:) Bob Hagel would be proud as would Warren
 
The WSM is still being chambered though in factory rifles. Also Hornady just released Factory ammo offerings in the Precision and Outfitter lines! I think one is the 150CX and the other the 162ELDX.

The issue for me was getting high quality brass, If Lapua, ADG, Peterson or other match grade brass was available, I'd still be shooting and hunting with a 7WSM. Both of my custom rifles in 7WSM have been rebarreled in new chamberings.
 
This is a very interesting design. I love the 28 Nosler but always felt like it had too much case capacity. I could never find a powder to get close to 100% fill without being over pressure. Your design looks just about perfect and would fit in a DBM. As Rflshooter mentioned, I would make the neck longer to keep the base of the bullet out of the powder column when using heavy for caliber bullets. Please keep us updated on the progress.
 
The issue for me was getting high quality brass, If Lapua, ADG, Peterson or other match grade brass was available, I'd still be shooting and hunting with a 7WSM. Both of my custom rifles in 7WSM have been rebarreled in new chamberings.
I recently stumbled on 200 Pieces of new Bertram and I have some new Winchester also.
 
Wyatt's makes a .400 length internal mag box.

162-168 at 3250 fps is awesome at 1200 yards, neck size the 7 Mashburn Super brass that is Winchester formed from 300 Win Mag. 3350fps is max for the Mashburn getting accuracy with long brass life, great 300 Win mag brass is available Now. C&H has Mashburn dies.

For 500 yard shooting, the 150g Nosler ballistic tips never quit amazing me in how well they killed from all angles.

With 175s, the 7 Mashburn is doing 3050-3100 in the accuracy node with 10+g less powder than the 28 Nosler or 7 STW, with Winchester brass. A friend is shooting the 150g Nosler ballistic tips at 3500 in his Mashburn with a 28" barrel.
 
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