General O'Neill seems to have a Purple Heart medal in a frame on his wall. He never wears it on his dress uniform even though he's been wounded several times on the show.
When Col. Reynolds fires his shotgun at the replicator that is on a computer console, the replicator blows apart, but there is no damage at all to the console.
The "blast door" flexes when Reynolds pushes the C4 against it.
The firearm that Colonel O'Neill first uses when the Replicators attack Earth is actually a shotgun, not a grenade launcher.