Actually, I think even the 4" would work for most guns. Abolt action is toughest, but if you remove the floorplate and magazine, it is pretty small, and will hang in the oven much straighter and more stable without the floorplate. Getting the heat into the pipe is the only problem. Some sort of expander/reducer may be the way to go.

With the fiberglass insulation, you could probably use single wall black stovepipe. Just be sure the fiberglass has no combustible inner layer. Might get a smell from the binder in the fiberglass, the first time firing it up. Water heater blanket insulation would be he right stuff.

TC1,

Got the 5" double wall, top, and eye bolt. Have not gotten another hot plate yet. Do have one already. Will check the diameter of the element.

Did you have to make an adapter to locate the hot plate element within the tube?

Hope a 36" tube is long enough for a barreled action.

That is indeed what is known as "B-vent" pipe. A pre-formed double wall galvanized steel pipe. I have seen it available up to 10" sizes. Look in your local phone book for Heating and Cooling Equipment Wholesale Supply company and see what they have.

One thing I did used a combination of the pipe method and an old electric stove. Most electric stove tops have an oven vent built into the left rear burner. I pulled the eye out, cut and wire nutted the electrical connection for that eye, used a hole saw (5 1/2") and 2 small sections of b-vent. B-vent has a male and a female end, I cut off the female end of a short (12") piece and made a flange and rivetted it to the deck thru the hole I made. Some hi temp mastic on the top side sealed it up a bit. The other (24") piece of b-vent I bought locked into place with an 1/8th turn and I insulated the bejeezus out of it. Made a top from sheet metal and insulation, with a small tube (1/2" galv nipple) on top attached with 2 electrical connector nuts for a vent (figured there was a vent there to begin with).

I could still use the cook top for Amerlene Parkerizing and for boiling carding water, and the oven for small parts was same same. That contraption has long since bit the dust and now I use a converted BBQ grill. It keeps a steady 400 for powder coating if I need it.