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 on the 257 Roberts case necked down to .22 cal with no other changes. In a write-up in a book “Rifles – A Modern Encyclopedia” in1958 he wrote the following: “The .228 as I originally made it is nothing more than the .22 Niedner. At the time I had never seen the .22 Niedner and simply necked down the .257 case, but I later found out that the .22 Niedner was a 7mm (x57) case necked down to .22, which make the cartridges identical except for bullets. I used a 90 grain and he used a 70 grain.”  See also the 224 Texas Trophy Hunter.

Source: Zeglin, F; – P.O. Ackley – America’s Gunsmith