If you could design a cartridge from scratch

[Calvin45]

And a truly monstrous 6mm is conspicuously missing in the world. I'm talking bigger than .240 weatherby or 6-06.

I've enjoyed reading about the old .244 H&H cartridge which is exactly what you think it is, as well as the 6mm-264 win mag dubbed the 240 incinerator or 6mm Mach 4. But what i think might be fun and semi new would be the weatherby RPM case necked down to 6mm. Could be a very light very flat combo.

 

[Calvin45]

Legitimize the .470 capstick and the .550 magnum (a straight walled .378 wby case, google it if your unfamiliar, it's awesome) as factory rifles. Very limited market but dang those have cool factor for me.

 

[Calvin45]

I promise I'll stop posting for a bit after this haha, but the other idea I've had is a modern old-school belted Weatherby magnum with the curvy shoulder. The .350 or 6.5 rem mag case necked down to .224" with a long neck and given that double radius shoulder and some freebore to let it scream. Monster .22 with some flare. I hope Weatherby makes this idiotic cartridge as it makes little practical sense but would be seriously impressive. Not past the realm of truly useless case size either, I read of .22-06 and .22 RSAUM (dubbed .220 redline), would be similar to the well known .22-284 wildcat as well. But I want that classic curvy shoulder and a weatherby headstamp

 

[epoletna]

Calvinr45:

I take it you think the curvy Weatherby design adds something in the way of burning efficiency. If that's the case, why not put the curvy shoulder on a standard .30-06 case? Would that improve powder burn, or does it need to be a fatter powder column?

 

[VinceMule]

Calvin, there is a guy on this site building a 6/280 AI for heavy bullets, this should be very interesting.

 

[DTubb]

5/35 SMC 2004 Elliptical shoulder on a 20 cal bullet on a 6BR case with a 1.5" case.
Bullet diameter in relation to Cartidge base diameter approaches 2.5 to 1.
So based on that a 1.75" case with a .585 diameter head shooting a 6mm bullet would be the next step up.
Needs a case full of slower burn rate powder.
By Smalley sent me a 6mm elliptical shoulder reamer using 6XC case with a .284 case diameter held short.
Didn't see enough velocity increase to warrant any further experimentation.
SMC= Bryan Smalley & Chuck Mcpherson

 

[Calvin45]

Calvinr45:

I take it you think the curvy Weatherby design adds something in the way of burning efficiency. If that's the case, why not put the curvy shoulder on a standard .30-06 case? Would that improve powder burn, or does it need to be a fatter powder column?

I actually don't really think the curvy shoulder makes much of a difference it's just neat haha

That being said I've wondered about fiddling with these things. Biggest issue I'd see with the .30-06 case is headspacing…the belt helps, I've often wondered how well the curvy shoulder headspace's for those who just neck size things.

As far as how fat the powder column is…I mean weatherby put that weird shoulder on their .240 magnum which is in essence a belted .30-06 case.

 

[Calvin45]

5/35 SMC 2004 Elliptical shoulder on a 20 cal bullet on a 6BR case with a 1.5" case.
Bullet diameter in relation to Cartidge base diameter approaches 2.5 to 1.
So based on that a 1.75" case with a .585 diameter head shooting a 6mm bullet would be the next step up.
Needs a case full of slower burn rate powder.
By Smalley sent me a 6mm elliptical shoulder reamer using 6XC case with a .284 case diameter held short.
Didn't see enough velocity increase to warrant any further experimentation.
SMC= Bryan Smalley & Chuck Mcpherson

Okay first of all…are you who I think you are?!?!? If so, big admirer of the scientific advancement of our shared interest you've pursued

Second of all…what is an elliptical shoulder?

 

[VinceMule]

Calvin, there is no advantage in stopping brass flow past 37*.

 

[Calvin45]

Calvin, there is a guy on this site building a 6/280 AI for heavy bullets, this should be very interesting.

I'm familiar with that, have chatted with him about it. Probably the practical upper limit

 

[DTubb]

Okay first of all…are you who I think you are?!?!? If so, big admirer of the scientific advancement of our shared interest you've pursued

Second of all…what is an elliptical shoulder?

SMC case design requires a hemispherical shoulder (round In appearance) and a longer neck.
Thanks

 

[asd9055]

I actually don't really think the curvy shoulder makes much of a difference it's just neat haha

That being said I've wondered about fiddling with these things. Biggest issue I'd see with the .30-06 case is headspacing…the belt helps, I've often wondered how well the curvy shoulder headspace's for those who just neck size things.

As far as how fat the powder column is…I mean weatherby put that weird shoulder on their .240 magnum which is in essence a belted .30-06 case.

I believe the double radius increases burning efficiency, especially for large capacity cases. Just think about flow through restrictions and how different angles affect it.

 

[epoletna]

Calvin45:

Agree with everything you said, although I thought there was some problem with belted cases separating just forward of the belt?

I used to reload both .219 Zipper and .30-30, and neck stretching on both of those was significant. I always assumed it was due to the long gradual shoulder. Put a sharper shoulder (35*-40*) and you get less shoulder stretch. Maybe not, but that was my theory.

 

[Calvin45]

Calvin45:

Agree with everything you said, although I thought there was some problem with belted cases separating just forward of the belt?

I used to reload both .219 Zipper and .30-30, and neck stretching on both of those was significant. I always assumed it was due to the long gradual shoulder. Put a sharper shoulder (35*-40*) and you get less shoulder stretch. Maybe not, but that was my theory.

That can happen with belted mags but I guess I've been lucky. I run my .257 wby, 300 win mag, and 358 Norma hot and have never had this happen personally though I do carefully inspect cases after each firing. To be honest I often find the first thing to give up besides primer pockets after numerous firings is neck splits on belted and other cartridges. I don't anneal, no big mystery there.

I've heard that theory too. Some truth to it up to a point tho in a conversation I've had just shooting the breeze with Fiftydriver he's relayed his vast experience with 6mm wildcats to state that he didn't really notice any difference in brass longevity going from 6-06 to 6-06 ai which certainly goes against that common wisdom you mentioned.