Oh hey, here are some pics of a parent cartridge case (the .250 Savage) and its derivative wildcat, the .260 Savage Ackley Improved.

...ooops! I meant "the 6.5 Creedmoor." Same difference.

Take the old .250-3000 Savage case, apply Ackley improvements to increase case volume, and neck it up from 0.257 to 0.264... this is the result. I think you could use .250 Savage brass, neck it up using a Creedmoor neck sizing die, and fire-form the case body into the chamber.

Please pardon me for never noticing this before.

And now I want to invent a 7mm cartridge in the same fashion because I'm kinda silly that way.

-AaronB

About 30-35 years or so ago, I had a left hand Remington 700 barreled to 6.5x250 Savage, with no other changes. I ordered dies from Redding, back when they used to serve their customers that way, and the tech I spoke to on the phone kept urging me to use the .300 Savage as the parent case, which pretty much accomplishes what you are suggesting, a short, improved case.

I really only wanted to duplicate the performance of the 6.5x54 MS cartridge, so I was already over capacity to do that, but shrinking the case down further would have meant using .35 Remington brass, which coincidentally is pretty damn close to the Mannlicher case. Wheels within wheels…..

Not too long afterwards, Remington released their .260 cartridge, so really I was just counting how many angels can dance on the head of a pin.

The whole idea behind the 6.5 Creedmoor initially was not as a hunting round, but to give good long range target performance with a 6.5 slug in a package that would fit in a short action magazine better than the .260, and provide less felt recoil than a .308 whilst doing so. That it became the darling of the hunting fields can only be attributed to the feminization of men. That last part is a joke.

6.5x55 Swede, .260 REM, 6.5 Creed, all are just pages from the same chapter. After my expensive exercise with a pretty much redundant wildcat, I barreled a medium action Sako to 6.5x55 and never looked back.

Otony

I figured that, the cartridge dimensions being what they were, one could run a well-lubricated 6.5 Manbun case into a .250 Savage full-length sizing die and voila! Out would pop a newly-minted .250 Savage case with the incorrect headstamp.

Having nothing to lose but one piece of rifle brass, I went ahead and tried it. I had to lean pretty hard on the handle of my Texan single-stage press, but nothing broke or got stuck. The resulting case had a few shallow dimples in the shoulder, but those would fire-form right out upon first usage in a .250 Savage.

So, for future reference, if I can't source .250 Savage brass, in a pinch I can resize the 6.5 Creedmoor and use that. Politics and reloading both are the art of the possible.

-AaronB

The 6.5x57 Mauser is just what it sounds like... a necked-down 7x57. It's apparently been a popular hunting cartridge in Europe for years. I have a rifle that was originally chambered in that caliber, before it got rebarreled.

-AaronB