The H&R/NEF owner's manual mentions using any ammo that isn't loaded to SAAMI and ANSI specs, milsurp isn't, so they indirectly say not to use milsurp in any H&R, but they also warn against using handloaded or reloaded ammo too.
Tim
http://hr1871.com/documents/manuals/HR_NEF_HANDI_RIFLE_MANUAL.pdfThis firearm was manufactured by H&R 1871, LLC, and has
been tested using proof and service ammunition that meets
Sporting Arms & Ammunition Manufacturers Institute
(SAAMI) & American National Standards Institute (ANSI)
performance standards.
H&R 1871, LLC assumes no liability or responsibility for injury or
damages resulting from misuse, neglect, alterations, the use of
parts not of our manufacture or the use of ammunition that is
faulty, handloaded, reloaded or not made to the above standards.