If buying new, I'd be happy with either the Lyman or RCBS. I've never had a RCBS, but haven't heard of any ill's about them. I've been using a Lyman Mould Master XX 20 lb lead pot since 1979, only problem with it I've had is the thermostat going out on it around 6 years ago. Lyman had discontinued that model and sold out of it's remaining stock of replacement ones, but gave me the phone number of a shop in Missouri that had replacements. Got one, wasn't an exact one, but the guy at the shop advised it was better than the original. Sent a diagram how to rewire and the XX has been 'spittin' out lead since. I was just to 'cheap' to buy a new one for some $250+ greenbacks. New thermostat was around $45.00. I did tell Lyman they should still be stocking the XX parts.
Navy Six: I noticed when that when my original thermostat was going bad, the top portion of the furnace seemed to have lead at the right temp, but the bottom area (pour spout area), seemed to not be the right temp and would keep plugging up no matter what I did. That was before I invested in a lead thermometer, so I can't say what the lead temp ranges were. As long as were talking about 'plugged' casting pots, this post isn't a"Plug" for Lyman products, but I think they have good stuff, no matter what model you get.
Agree with Wildman on the 'dentrites', it isn't furnace problem, but rather 'a price of doing business' when you cast. I've always done the same as Wildman, but fashioned a 'unplugger' from a wire coat hanger. Bent a piece of the hanger at 90* leaving around a 1" or so for sticking up into the pour spout, then I shaped the remaining length into a oval shaped handle and "WahLaa", you have an indispensable casting tool. I've been using the same one since buying the Lyman Furnace in '79. Casting bullets with lead pots is the same as plantin' a garden, there are things that need to be done with the garden after planting the seed to get good veggie's---meltin' lead for bullets is more than just turning on the juice for the pot and pouring bullets, ya gotta treat the lead and pamper it to get good bullets. Readin' this post tells me its suppose to be 50* this week in Ol' North Iowa, maybe time to start castin', need them bullets!!
Got to thinking after I posted this--Ya-I'll "Plug" Lyman products, have an assortment of Lyman, ie. moulds, dies, etc. Never a problem with any except the XX Furnace, but the thermostat didn't go out until nearly 30 years of service. Paid $50.00 new for the unit back in '79!