If you're only hanging one steel gong, the Tripod bracket is a sturdy but lightweight system; using your three lengths of 2x4 to make the stand. The bracket is made of AR500 steel, but only 1/4" thick; it should stand up to plenty of shrapnel, and hopefully a couple of direct hits by rifle rounds.
We sell the bracket alone, or bundled with an AR500 target. If you buy it with a target, not only do you save a couple of dollars, but we'll include a bonus length of dirty, old, heavy fire hose to hang the target. The fire hose is 'experimental'; we'd be interested in your feedback.