So no disrespect to Tennyson intended, "In fall an older man's fancy lightly turns to thoughts of more shooting projects."
Why a 24 Mamba? Cheap brass, cheap bullets and unbridled hubris that we can concoct the "universal round" that no-one else has been able to create to date! (I warned you it was unbridled.) Being the cheap ******* I am, I can preserve my investment in my 223 Short project rifle and just change barrels if I don't want to get a new rifle. Also the 223 Short is winding down for me when the final load testing is completed, hopefully by Spring 2018.
Short team AZ member George A's research has led us to understand that thru a case redesign using a larger case capacity, using new powders and bullets, a 30º shoulder to enhance accuracy and ignition, and using a Wylde throat specification that supports accuracy and higher pressures, we can build a single rifle that can excel at any varmint shooting, ethical large deer harvesting at extended ranges, and long range target shooting, while using 40% less powder than the 243 and 5% less than the 6mm BR.
What is the 24 Mamba?
A modified 6x45 that does not require a big investment in reloading gear or supplies to adopt it.
A 6x45 is a 223 Rem case necked up to 6mm/243 with no other changes.
The new design can use the cheapest and most common once fired brass; will need a custom PT&G finish reamer costing less than $200 for the team to purchase; will need a new barrel to be chambered; will need a neck expander before cases are fire formed; will NOT need custom dies; will be easy to develop loads for because of pre-existing data from the 6x45; will be economical to shoot for any required task.
The basic 6x45 design was revised until we reached a 6x45 + 8% case capacity, which brings it close to the classic benchrest 6PPC case capacity. George ran the numbers to discover the performance potential of the design.
A regular 6x45 has a standard 223 Rem .376 case body base and a standard .354 minimum taper, a standard 23º shoulder and a longer than standard neck length of .225", a standard 1.438 base to shoulder, and a standard 1.76 case length.
The 24 Mamba has a standard .376 case body base (0%) and a .369 minimum taper (-1.5%), a 30º shoulder (+30%) and a .203 neck length (-10%), 1.478 base to shoulder (+3%), and 1.76 case length (0%). We get the extra base to shoulder length from the 30º shoulder which is much shorter than the 23º shoulder, and the .020 neck length reduction adds to the case capacity.
We have not determined the maximum cartridge overall length yet.
Welcome aboard and stay tuned.
P.S. In pursuit of a more recognizable name for this new cartridge design, and in keeping with the team's first project recent official name change from the 223 Short v2 to the 22 Mamba, we decided to rename the 6x45AL, the 24 Mamba, in a direct reference to the small and deadly snake that bears the name, which is also known as "The Kiss of Death".
There are a few of common features the first two Mamba cartridges share, but we do not know if we will adhere to these with future designs. A 30º shoulder, a 0.007" case taper, a slightly shorter neck than is typical for the caliber, a 223 Remington parent case.