I strongly suggest care in using this technique. Most metal minis, especially Reaper are made of a tin alloy (90-96% typically). The melting point of tin is 449 degrees and some alloys can lower that point to as low as 394 degrees. The "cure point" tends to be around 250 degrees for most of these alloys. In a 250 degree oven, it can be possible to distort the details on the mini if the metal has lost its cure. On the other hand, I have used this type of dry curing method on tin before to ensure a smooth phosphorus coat before electoless copper coating. 200 degrees should be theoretically safe, though.