Choke sleeve installation

I have an old Steven single shot 12 ga shotgun. The ID of the barrel to too large for a typical choke tube installation. It's .742 diameter. I tried putting on a Polychoke, that was removed from another shotgun. The installation went well, but the gun shot way low, likely due to the bulbous choke at the end of the barrel, along with the corresponding high front bead. I bent the barrel upwards considerablly, but still was low. If it was painted yellow, it could be mistaken for a banana. Anyhow the Polychoke has to go. After removal and straightening the barrel, the POI was restored, but I now had a cylinder choked barrel.

I see that Numrich has Nu-Line choke sleeves for sale. No external dimensions are given, just internal. .720 ID was the size I was interested in. Has anyone ever installed one of these? If so, how was it secured, silver solder, acraglas, or some other means. The barrel is .935 OD, which is rather thick, giving a .096 wall thickness. If there was enough thickness in the choke sleeve, I was hoping to open the inside end to .742, and taper back to the original .720 size. The sleeves are 2.5" long. I have a lathe, so the machining should not be that difficult, once I know what to do.


https://www.gunpartscorp.com/products/1198620

Am interested myself.
I would try contact them and see what they say. Usually for me, they have been good to measure certain things and let me know. I'm sure they could do the same here.

You could also try a Jug choke as they work well with muzzleloaders. See the sticky on V M Starr. He was the expert on the jug choke process.

I had contacted Numrich before I purchased the sleeve. I was told the sleeve is .793 diameter. I purchased the sleeve, and found their information was correct. The mouth is .750, which should handle any oversized bore. I used JB Weld to secure it in the barrel. I shot the gun about 50 times, and it did not move. The installation process was easy. Just be sure to indicate off the bore, before reaming, not the barrel.