I had a customer come into the shop with a choke tube stuck in a Winchester shotgun. He had NOT folloowed instructions and had screwed a choke tube with preservative grease and NO lube into the gun and had then shot it about 1000 rounds. He broke his tool trying to remove the choke. I soaked it in Kroil and tapped the barrel with a lead mallet and then broke my heavy duty tool and the choke wouldn't budge. Now Brownells sells a tool with knurls that bites into the iinside of the tube and will remove any thing, but they are $125.00 each and you ruin the tube. So I went to work. I annealed a file and ground and polished a shank to fit in the tube and then ground ears to fit in the choke tube notches. These ears were ground and filed to be an exact press fit. I then re hardened the tool and put a handle on the file so I could press into the choke. I then put the barrel in my barrel vise just behind the choke tube and pressed the tool into the choke. I then put on a 12" cresent wrench to the flat of the file and cranked. It came loose with a pop but did no damage to either the choke or the barrel. This was THE toughest choke tube I have ever had to budge. If anyone else has this problem let me know and I will send drawings of the tool.
I will note that I mounted the barrel in a bushing made from oak that was relieved for the vent rib. I had to rosin the block to keep it from turning.