I was firing up a propane forge I just built last Tuesday in my garage over in Akron, and the burner backfired so hard it sent a fireball right into my wood workbench. The flame caught some oily rags I had set near the far edge, and it took me a solid 3 minutes to smother it with a welding blanket. I lost a set of tongs to the heat and a lot of respect for cheap regulator fittings, so what safety checks do you all run before first light on a new burner setup?
What was the regulator rated for, and did you check it against the burner's actual draw before you lit it? Cheap fittings love to pass more propane than the burner can handle, and that backup in pressure is exactly what causes a backfire like that. Also, was the burner mounted at the right depth in the forge body, or did you just eyeball it? Getting that tube too deep or too shallow can mess with the air mix and blow flame right back out the intake.