Forgive the stupid question but what would this be called, once I have a name I can do a search and gather info... .308 necked down to 6.5mm with an improved chamber? Is that a 260 Improved? How would it stack up to a 6.5-06 Improved? I am trying to work something off a short action, in a 6.5mm.

Thanks
Frank D

I'd be a little slower. If you want to go that route, find one of the good long range smiths and see if he has a 6.5/284 reamer.

The cost of the dies and chambering would be less, and it would perform about the same as the '06 version. It would not hurt to check with someone like Bill Shehane. HTH, Dutch.

For a short action 6.5mm equaling a 6.5-06, the two common options are the 6.5 rem mag, and the 6.5-.284.

I am not a fan of the improved rounds, the velocity gains are minimal, especially on the 308 case. If you want more speed, go to a signifigantly larger case, not a marginally larger one.

Frankd,
The .308 Necked down to 6.5 has been around since the late 50s or early 60s. As soon as the military T-65 7.62 Nato cartridge came out in the 50s (commercially known as the .308 Win), it was necked to all sorts of things. The original cartridge (6.5-.308) was called the .263 Express (this info is from P.O. Ackley's book Handbook for Shooters and Reloaders...this is an excellent reference on wildcats).
The .308 case IS an improved cartridge of sorts. It has minumum taper. The shoulder is shallow apparently to make it easier to manufacture on automated equipment. Going to a sharper shoulder would not even give you 5% increase in case capacity.
Of course, this cartridge is now a factory number in the .260 Remington. This is a great little cartridge.
As a previous poster suggested a maximum performance short action cartridge would be the 6.5x284. Norma makes properly head stamped brass and this cartridge in the new darling of the small bore long range shooting crowd.
I personally shoot a .256 Newton custom (in the 1988 Gun digest under custom guns). The 6.5s of any persuasion really give great killing power (especially with the 140 gr Nos Partitions) all out of perportion to their size.
In summary, I would stick to the .260 Rem or the 6.5x284 and stay away from an "improved" .260 Remington.
Hope this helps,
The Bearman out in Montana Territory