General help with rocket-stove style stove - can I get temps low enough to use all metal safely?

Total newbie needing help getting my bearings on the language and technicalities of building rocket stoves or something similar.

I'm planning to be building a simple stove made from a 55 or 30 gal  drum and a bunch of stovepipe.

My plan is a drum with a hole cut into the bottom side, about 6-12in up the side. In that hole will be placed an L-shaped stovepipe making a horizontal feeder that bends in the center of the drum, and opens up near the top of the (closed) drum. Near the bottom of the back of the stove will be a chimney, in an L curve towards the ceiling. The idea is to have airflow go from my feed tube, up the riser into the drum, and then spiral down for extra burning through the drum, and out and back up through the chimney at or near the base.

My intention is very little insulation. I imagine my feed tube will be insulated where it sticks out of the drum, and my chimney may be insulated (more research to be done), but given the go-ahead from those who are more educated than myself (maybe that's you) I would have my drum not at all insulated. My understanding is that while this will not allow complete burn, it will keep the temperatures low enough that having a metal riser and chamber shouldn't be a problem. Is this an accurate assessment?

I'm also considering using a copper pipe coil around the outside of the drum for a thermal syphon to make hot water for my showers/dishes/etc.

And stacking rocks without mortar around and near the drum to absorb what heat it does, intending to work as a mass that does not fully insulate the drum.

Thoughts? I have a lot more research to do, but I'm having trouble finding the information I need to get my bearings.

This is meant to be a stove specifically for heating an insulated bus, so I shouldn't need extremely high heats, and my other option is a basic wood stove (costs money) so while in an ideal world, and with more time to build and source cob before winter, I would have complete burn and more insulation, I don't want or expect to have anything like that at this point.

My main concern right now is wether I can keep temperatures low enough to use a steel drum safely, without weakening the metal.

If I understand your design correctly, your fire will be burning inside stovepipe? If this is the case, it will probably burn out relatively quickly. The drum should be ok; the temps there should be cooler as there should not be any burning going on in it. I would make sure the chimney has a good draw to prevent smoke-back.