Best Cartridge Designs?

[Will Henry]

I knew several shooters who shot .125 shortened BR’s, and they were very accurate. Many used them because they were still using accurized REM actions with the .473 bolt face. Many of these were in Davidson sleeves.

The biggest drawback to the BR short is the PPC is so easy to make. You just turn the necks, (if needed), and fireform it.

With the BR, you have to push the shoulder back with an appropriate die, trim it back, turn the neck, then fireform it.

When it’s all said and done, I’m not real sure the shortened BR isn’t just as capable.

In this, it all comes down to powder capacity, does it not? Powder capacity and the ability of the cases to handle pressure. Both the PPC and BR cases can handle a lot of pressure. I think this was the main issue with the old 6x47; just about the time it was starting to perform well, the primer would fall out! The PPC let you load a little hotter and the brass would keep on going. Even the early 220 Russian brass, with the thin web, allowed a step up from the 6x47. My best 6x47, which was very good, had me tossing brass after a half dozen firings, when the pockets got loose. I could shoot PPC brass forever! WH

 

[davidjoe]

We might use a “Hemi” shaped chamber if we wanted all the pressure to build inside cartridge shoulder area as efficiently as possible, but that would be to direct force toward its focal point, which is the wrong way for a bullet, but great for a piston.

We ultimately want it all moving the direction of the bullet, the the degree of loss TW describes is both the inefficiency of some cartridges next to others and the fact that we don’t have the pejorative phrase “bottlenecked” for nothing.

The true combustion chamber in which the gas expands is the combined shape of the cartridge and the bore.

Powder to gas is a 300 fold increase in volume. Most of the actual combustion chamber by volume is the bore.

 

[ASbobcat]

OK my perfect case design. .010" taper per inch on the body, 30 degree shoulder- all to facilitate FL sizing. Neck length one caliber+. You fill in the capacity required to shoot the bullet of choice at the velocity you want. That formula has worked for almost 30 years.

Remember rule #1 in my shop is "Don't do anything to make the phone ring".

Excellent points.

I got suckered into the 6Dasher hype, but have returned to the 6BR.

40deg shoulders have only one advantage, less trimming. The disadvantage, as you point out, is shoulder bumping. And chambering a 30deg shoulder is more forgiving if the shoulder is not correctly bumped. Also, the greater turn angle at the neck/shoulder junction promotes formation of a doughnut, which requires neck turning. So you've just traded trimming for turning. Pick your poison.
Less body taper in "so called improved" case designs also risks less chamber wall to body clearance, which chances case stretching. All bolt thrust should be born by the case head, not the case sides. ( I recommend that everyone read read "Varmint Al's" treatise on this subject, He's a former "rocket scientist" from Sandia Labs.)

Longer necks are more conducive to proper bullet alignment.
6BRX, a joke.
6Dasher, a fantasy.
6BR, a thing of beauty.

 

[Bottom Fodder]

I was thinking I’m short, fat with sloping shoulders and a big head so in theory, my body is basically shaped like an accurate cartridge lol

 

[Fuj]

I got suckered into the 6Dasher hype, but have returned to the 6BR.
6Dasher, a fantasy.

I know a few people that shoot the Dasher and would not go back
to the 6br. As it is I had made several long neck Dasher cases for
discussion. I left the necks at a 3/8" long then would let the person
trim too length what was needed for their needs. I have too many
other things going on to pursue it but, I may pull it off the back
burner and turn it into a 30.

 

[ASbobcat]

I was thinking I’m short, fat with sloping shoulders and a big head so in theory, my body is basically shaped like an accurate cartridge lol

When you blow your top, you'll be on target.

: )

 

[Bodhisafa]

I know a few people that shoot the Dasher and would not go back
to the 6br. As it is I had made several long neck Dasher cases for
discussion. I left the necks at a 3/8" long then would let the person
trim too length what was needed for their needs. I have too many
other things going on to pursue it but, I may pull it off the back
burner and turn it into a 30.

What did you not like about the Dasher?

 

[Fuj]

What did you not like about the Dasher?

I did the work for someone else. I don't shoot a Dasher. The guy's
I know, shoot the Dasher at Ridgway's 850/1000 yard VBR.

 

[Infrequent Shooter]

Start with conventional 243 brass and give it a 30 degree shoulder?

 

[alintx]

I'm of the (mostly unfounded) opinion that case design is mostly about capacity, and that certain features contribute to quality of life, utility, and brass life. You can make just about any common case shoot really well if it's the right size for the bullet/barrel you're using. A good sharp (30ish degrees) shoulder and relatively straight taper with a long enough neck to avoid the donut are all positive features in my book.

What I don't believe (again, anecdotal) is that within reason the case geometry impacts ignition or barrel life. I would happily be proven wrong on that, but it just doesn't seem to matter.

Ppc kind negates that statement

 

[Dgd6mm]

Start with conventional 243 brass and give it a 30 degree shoulder?

6mm Competition Match, 6SLR, .243AI.

 

[Infrequent Shooter]

6mm Competition Match, 6SLR, .243AI.

if I use a 243 Redding die set, what is the next step, if there is one, from this starting point?

 

[Dgd6mm]

Whoops. I replied and should not have without keeping up with the thread.
Please disregard my post.

 

[J.d. Popkes]

7-6.5 PRCW’s definitely don’t rule F open class. In fact, I’ve only seen one 6.5 PRCW in competition in the last two years.

Soon

 

[Dave M.]

Seems this is the way of the future. 7PRCW are taking over the world. lol.