Here you go.
From the NRA Highpower Rifle rulebook:
3.1.4 Foreign Service Rifle - Any center fire, self-loading rifle, as issued
for general service by the armed forces of any nation (except rifles described
in NRA Rules 3.1, 3.1.1, 3.1.2 and 3.1.3), or the same type and caliber of
commercially manufactured rifle, having not less than a 4 1/2 pound trigger
pull, with standard type stock and standard leather or web sling. In all courses
and in all positions the standard 20-round or 30-round box magazine will be
attached. A hinged butt plate, if installed, will be used only in the folded
position. The gas system, if any, must be fully operational. External alterations
to the stock will not be allowed. The application of synthetic coatings, which
includes those containing powdered metal, to the interior of the stock to
improve bedding is authorized provided the coating does not interfere with the
original design, but may vary in dimensions of rear sight aperture and front
sight blade. The internal parts of the rifle may be specially fitted and include
alterations which will improve the functioning and accuracy of the arm,
provided such alterations in no way interfere with the proper functioning of the
safety devices as manufactured. Such rifles will be fired in the NRA Match
Rifle Division.