I've done a fair bit of front loading the shafts using 1/8" lead wire. It is 35 grains per inch, heavier than any nail and quite cheap. Tungsten is heavier, but too expensive for me. I drill my shafts with a jig in a drill press rather than a drill guide. Drilling a 2" hole is pretty easy, 3" seemed to be the practical limit. You would need only an inch or less with the lead wire. A brad point bit helps with drill wander. Filling the ferrule with shot, solder, etc. works, but to get 30 gr you will lose quite a bit of the ferrule's depth which can lead to alignment and strength issues. I didn't like it.
Considering the time, effort and cost involved, new 160 gr heads is a pretty reasonable option, or just leave your arrows a little long.