Cartridge by Ken Howell, based on the 30-06 case, but lengthened to 2.6" as opposed to 2.494" for the standard 30-06.

The 338-378 KT was designed by Elmer Keith and Bob Thompson in the 1960's as a long range elk cartridge to be used with slower burning powders available at that time. They kept the Weatherby double radius shoulder but shortened the case 1/4" to better suit case...

Wildcat based on the 284 WIN case. Designed by Hawaiian based gunsmith Mark Pinkston and manufactured by Kailua Custom Guns, Hawaii this was an attempt to offer a 338 cal rifle for carbines.      

   Developed by David Tooley, this is basically a 338 Lapua Improved

   Developed around 2007, the 338 Xtreme (338 XT) is based on the 505 Gibbs case with a 35° shoulder.

     Interesting box that came out of Zimbabwe. The crest on the box bears resemblance to the SLADE Family Crest, but I have not found any other info on who Nimrod Cartridges were.  

   Prototype round by Winchester resembling a current factory load. the other one is the 264 Winchester prototype

The 338 Whisper is part of a range of cartridges developed by JD Jones from SSK Industries. The parent case is the 7mm Bench Rest, necked up and fire-formed.      

   The 338 Thumper is one of a new line of cartridges by Subsonic Hunter in Winter Park, Florida designed for hog hunting.

      Like the .458 SOCOM, the .338 Spectre cartridge was developed specifically for the AR-15 family of gas-operated, detachable-box magazine-fed firearms. The cartridge is intended to fill the gap between traditional pistol caliber cartridges and...

The 338 Snipe-Tac was developed in 2001 for extreme long-range hunting and target applications. The parent case is the 408 Chey-Tac necked down and shoulder improved to 35 degrees. H2O capacity is a whopping 165 grains and velocity is well over 3,000 fps.   

   This is basically a 338 x 39 (or the 7.62x39 AK-47 case necked up to .338"). It is similiar to a current military cartridge used in Russia, namely the 9 x 39.

   Based on the 375 RUGER, the 338 RCM is a shortened cartridge, but with ballistics that will match the 338 Win Mag.

The 338 Reaper is an improved 338 Lapua and was designed by Dallas Lane from Lane Precision Rifles in Pocatello, Idaho.    

The 338 Razor is another cartridge designed by Alaskan ELR shooter Pro Martusheff (aka Swamplord) from Precision Rifled Ordnance. It is the shorter case version of the 338 Headhunter built specifically for Remington 700 and Winchester Model 70 actions. The case is...

Wildcat cartridge based on the 8mm Rem Mag case necked up to .338"   

Still under development as at Dec. 2014, it is based on a shortened 7.62x39 (AK-47) case, necked up to .338. This one is loaded with the Lehigh controlled fracture bullet.   

This is an improved version of the 338 Lapua for long range shooting.   

The 338 Headhunter is the longer case version of the 338 Razor and was designed by Alaskan ELR shooter Pro Martusheff, owner of Precision Rifled Ordnance who goes by the internet name of Swamplord. The Headhunter was designed as a single shot precision rifle to...

   Based on the 405 Win case necked to .338

Long range match cartridge based on an improved 8mm Rem Mag, necked to .338   

   The .338 Federal is .308 Winchester case necked up to .33 caliber. It was created by Federal Cartridge and Sako in 2006 and intended as a big game cartridge with reasonable recoil for lightweight rifles.

   The .338 Excaliber was introduced in 1994 by the A-Square company. The .338 Excaliber is based on a standard (not belted) rimless bottleneck case with the same rim diameter as the .378 Weatherby, but slightly greater powder capacity than the .338 A-Square...

The .338 Edge was designed by former SWAT/Narcotics officer Shawn Carlock in 2001 and was released after Remington brought out the 300 Remington Ultra Mag, but before the introduction of the 338 Ultra Mag. The 338 Edge is thus effectively a 338/300 RUM wildcat. With...

      Replica The 338 Dakota Short Magnum is a cartridge that saw the light at roughly the same time as the 423 Lapua in 2005 and apparently both were tested on a hunt in Tanzania. The 423 Lapua went on to be produced commercially as a joint...

Still looking for info on this cartridge, but it looks as if it is based on a shortened Chey-Tac case. Cases are by RCC Brass.    

   Ronald Brian McDaniels founded Black Mesa Rifle Company in Kenton, Oklahoma around 1992. The 338 Black Mesa was the second after the introduction of the 375 Black Mesa Express around 1993. Named after the Black Mesa, the highest point in Oklahoma.

   Created by Joel Russo and Bruce Baer based on the 408 Chey Tac case