I got a 1930-era military match .22 and over the years the front blade (dove-tailed into the bbl) has worked loose. What is the best way to remedy the problem? TIA.

Hello,
Might want to consider a slight peening/punch job on both sides of the dovetail, would not take much, to tighten the dovetail. Remove front sight, peen in/downward the two edges, drift front sight back into dovetail, should be good to go. Assuming rear sight is windage adjustable, set front sight up at mechanical zero, adjust right or left from rear sight.