Article I found regarding wildcats formed from the 338 Lapua..

http://accurateshooter.wordpress.com/2008/10/07/30-338-varmint-version-hits-4300-fps/

In our new article on the 30-338 Wildcat, you’ll find expert advice on forming the cases from .338 Lapua Magnum brass plus tips on selecting powder and bullets. The story also features some great photos of a 30-338 custom Richard Franklin built for a California client. That rifle is designed as an Elk Gun, shooting the 190gr Berger VLDs with Reloder 22 powder. The laminated stock is made from exhibition-grade Claro Crotch Walnut and Dennis Smith (aka the Stock Doctor) provided beautiful checkering and a hand-rubbed oil finish.

Ultimate Big Boomer for Varminters
Franklin has also pioneered an ultra-high-velocity varmint version of the 30-338. This cartidge achieves amazing 30-Cal velocities using long, very slow-twist barrels. Richard tells us: “I use 15- to 17-twist barrels with both the 300 WSM Varminter and the 30-338 Lapua Varminter. The 300 WSM easily gets 3900 fps with the Nosler 125 Ballistic Tip and the 30-338 Lapua will do 4150 fps easily with the same 125gr B-Tip. In the 30-338, the 130gr Barnes, a “ringed” bullet with grooves to reduce bearing surface, will get another 150 fps, topping out at 4300 fps. I find the 17-twist does a good job with the light bullets in the 30-338 but I’m going to try an 18-twist and a 19-twist to see if high velocity is a little more easier to obtain. I believe the 19-twist will beat any thing I’ve built to date for velocity and I also believe it’s going to be very accurate.”
The “Official” .300 Lapua Magnum
While nearly every 30-338 you see in the USA is a wildcat, manually formed by necking-down the .338 Lapua brass, there was an “official” version, the “.300 Lapua Magnum”. This was a factory 30-caliber cartridge based on the .338 Lapua Magnum parent case. Lapua produced enough factory ammo to get the .300 Lapua Magnum sanctioned as an official CIP-certified cartridge. QuickLOAD includes the .300 Lapua Magnum in its load database, and QuickDESIGN has complete CIP cartridge specifications. Unfortunately, the .300 Lapua Magnum is no longer in production. For you cartridge collectors, we’re not even sure if Lapua ever produced brass with a distinctive “300 Lapua Magnum” headstamp. However Vihtavuori does include .300 Lapua Magnum load data in the current Vihtavuori Load Manual. That reloading guide shows the .300 Lapua Magnum can drive a 220gr HPBT Sierra MatchKing at 2910 fps with a max charge of VV 20N29 powder. The .300 Lapua Magnum can push the 30-caliber 155gr Lapua Scenar at nearly 3500 fps with VV N170 powder. That’s impressive performance indeed!