And 50 cals one hundred meters on center along both southern and northern borders.
Don’t think that is very practical. Our border with Mexico is 3,145 KM long. Divided into 100 meter sections is 31,450 centers. Assuming a 3 man gun crew, to carry out your recommendation, would require 94,350 personnel on duty at any one time. To have a three section rotation on each 50 cal gun would require 283,050 personnel for the Mexican border alone. That figure does not include the 1,000s of support personnel needed to keep 283,050 troops in the field. The numbers are even larger for the Northern border. The border with Canada is 8,891 KM long.