Yep, thats it. Its nearly impossible to check melting point that way. Get yourself an infrared temperature gun. Put a nickle size lump of powder on a cast iron skillet (or something flat black and non reflective). Set the skillet on the stove and turn up the heat. Aim the laser on your temp gun right at the lump of powder. These guns are pretty accurate, and inexpensive. If there is anything reflective around the powder, like aluminum foil, it will not read correctly. Watch the digital readout and keep the powder in sight.
Testing like this my powders have melted within 5 degrees of the melting point