Hello

I was looking on some input on whether or not a rifled barrel liner could be flared at the chamber end?  I need the twist rate for the 32/40 black powder barrel 1-14" but I want to chamber for a larger diameter cartridge.  If the chamber area of the liner could be expanded to a diameter somewhat smaller than the chamber, then reamed as normal you would not wind up with the thin barrel wall around the chamber where you need metal most.  These liners are designed for straight wall cartridges, and they have limitations for anything ese.  Near as I can tell the liners are constructed from 4130 tubing, probably barrel quality stuff.  A blacksmith would make up a proper shaped punch, heat the tube to red heat and knock it in, but would the tubing tolerate this without splitting or structural weakening?

In the process ruining the heat treat of that metal, needing to HT again then re proof it before use again, hoping it didn't thin too much, If it works with out messing up the rifling grooves, did I miss something?

Yes, the possibility of the punched flare not being concentric with the machined bore.

Well for sure the heat treat is an issue, although as a rule barrel steel is rather softer than receiver steel.  A complete anneal and a slow cool down in the furnace is the general rule before any rifling is cut.  Definitely need a means to keep the punch concentric as possible, the belled section would have to be turned just enough to be trued up to the OD of the tube, the pilot on the chambering reamer in addition to being held centered by the tailstock trues the chamber to the bore same as always.  The rifling in that part of the tube is cut away in the process of cutting the chamber regardless.  The throating reamer tapers the bullet seat into the rifling at least 1/16 or so forward of the bullet bearing point, and no swelling of the tube is needed forward of the shoulder of the cartridge.  A matching cutout in the breech end of the barrel proper for the belled end of the liner with a lapped fit to avoid any air spaces...well that is all we can do.  I read that the difficulty of applying liners to higher powered rifles is they usually move.  This one ain't going anywhere, at least forward it isn't, and the pressures would be limited to suitable cast bullets. 

Awesome, it appears you have answered your own question. Good luck, you may need it.