[mr.c]

Martin: There is a huge difference in the hit from a "muffler gun" and a rivet gun. The rivet gun hits much harder than the chisel type gun. The rivet guns have a "teasable" trigger that can give you single hits if required. Rivet guns are sized by how hard they hit. They use a "X" suffix. A 1X is designed to set 1/16" rivets. A 9X will set a 9/16" rivet. The barrel length is generally longer on the more powerful guns. The gun that was used in the video appeared to be about a 5X (long thin barrel).
The 9X is a VERY powerful gun that probably would have torn up the mold used in the video. A 3X-5x would be more suitable for your purposes and more pwerful and controllable than any air chisel muffler gun.
You might also look into the palm held hammer made by Danair. They look like a palm nailer but here again, looks can be deceiving. The Danair hits very hard. Much harder than any palm nailer. We took mine apart at the Dixie Meet a couple of years ago to compare. Big difference. Sears used to market the Danair unit. I am not sure whether they still carry it. The Danair is a compact hard hitting tool. Ideal for flow forming. I think that they run about $350?