I'm not quiet sure what you're wanting but if im correct you're wanting unlimited rifle grenades? although you could do something like this in lua, I dont know the weapon# for axis rnade at the moment.
function et_InitGame( levelTime, randomSeed, restart )
et.RegisterModname("Rnade ammo")
end
function et_ClientSpawn( clientNum, revived, teamChange, restoreHealth )
et.gentity_set(clientNum, "ps.ammo", 42, 30) --allies rnade
end