Incorrect, the first production "inch" rifles were the Canadian C1 Rifle, on the outside it looked 'Metric' but was made to the 'inch' specifications. In fact the Canadian's where the lead on the conversion of metric to inch Specifications, They also deconstructed the FAL rifle and simplified many of the FAL production methods. These conversions/alterations were overseen by the Rifle Steering Committee (Canada, Britain, US, FN, then Australia
Joined and the US left). The C1 was introduced into service in 1956. 'Inch' Tool Room Models date to 1955.
T48 rifles made by H&S (500 Rifles utilizing advanced Canadian C1 Tool Room Model Plans) and High Standard (had to convert the Metric plans and specifications into American specifications and produce 12 Rifles to show their plans where workable all this for trials that happened in 1955.