Ok , found the thread and pictures , so , yes , they did. However , the mods were welded to the floorplate of the triggerguards and therefore non-detachable as we think of such .
First , air servive mag on an '03 sniper.
U.S. Springfield Model 1903 Bolt Action Sniper Rifle for Jim T..
Now the Bar mag modification.
03A4 with BAR mag?
HTH , Chris