Based on the 223 Remington case with a 40° shouder

   One of the predecessors to the 22 PPC, this one being based on the 223 Remington case, with a longer shoulder and steeper neck

   Based on the .30M1 case and resembles a 5.7mm MMJ, but with a more gentle shoulder. According to Dan Watters on THE GUN ZONE, the 223 Scorpion was the brainchild of Californian gunsmith Ken Bucklin way back in 1945. The above specimen is a recent remake...

   Relatively new wildcat

   Announced in 2002, the Winchester Super Short Magnum cartridges are intended to deliver a new level of long-range performance and accuracy to the .223 & .243 family of chamberings. Cartridge overall length is 2.36”, a half-inch shorter than the 2.80”...

Based on the 22 Hornet case. The first specimen below is with the original Sisk 50gr. bullet   

   info to follow

Resembles the 22 Dasher, but with a longer body and shorter neck. The goal of this exercise is to get as much speed as possible from the case/bullet.   

                            The 224 TTH was introduced by the Texas Trophy Hunters Association in 2000, but it was taken from an old idea...

This is a new development by Federal that was introduced in December 2017 as a definitive cartridge for the AR based platform. The 22 Nosler provided about a 25% improvement in velocity and 30% in energy over the existing 5.56 NATO round when it was introduced in...

   The original version of the 228 Ackley Magnum was developed by P.O. Ackley in 1938, although the idea came from around 1936 and was one of his first wildcat designs. He was looking for a better version high velocity .22 cal. rifle and his design is based...

The 228 Weatherby was never commercially manufactured and information about this cartridge is scarce. On the Weatherby.dk forum it is stated that the 228 was Roy Weatherby’s second development after the 220 Rocket and it was based on a shortened and necked 275 H&H...

The 24 Nosler was designed by Mike Lake, who is the Senior Manager of Engineering and R&D at Nosler. He was also responsible for the development of the 26 Nosler (2013), 28 Nosler (2015), 30 Nosler (2016), and the 33 Nosler (2017), all of which are based on the...

The HAWK line of cartridges were developed around 1988 by Bob Fulton. The 240 Hawk is basically a 6mm-280 Remington Improved   

- info to follow -   

Match cartridge based on the 243 Winchester case with improved 30° shoulder   

The .243 Catbird was designed as an ultra-long range 6mm varmint round. It is based on the .270 Winchester case necked down to .243 and blown out with a 35 degree shoulder.   

   "Improved" version (shoulder angle increased from 20° to 26.7°) of the 243 Winchester and about halfway between the ordinary 243 Win and the 243 Ackley

   257 Roberts necked down to 6mm/.243 cal (which is basically what the 6mm Remington is), however the 243 RC predates the 6mm Remington and the only difference is on the shoulder angle. Most shooters prefer the 6mm Remington because of the availability of...

PROOF Super (Australia) SOUTH AFRICAN HEADSTAMPS AND VARIATIONS   BOSS    PRO-AMM  

   The 244 Mashburn is an improved version of the 6mm Remington with a shoulder angle of 30° and minimum body taper

See notes on the 6mm Remington