Mr E.
I am working on SOMETHING similar but on a different rifle.

I ran across a Taiwan rusty eroded barrel for an M1icon Garand. I also popped for the Numrich M1 Garand castings... along with a demilled bolt... and even some Italianicon Beretta wood. While it makes an IMPRACTICAL conversion, all is good.

I ordered an "aircraft" drill... which is very long, to bore out the barrel, for a 22lr liner that I purchased via Numrich. I have the epoxy in which to set the liner. Epoxy is better than the old tyme solder. My only concern being getting the bore axis straight.

I have also watched the conversion process for 1903's... and was considering a conversion such as yours for a DP Enfield, until Mr. Peter Laidlericon convinced me othewise!

If you have a DP rifle, or suspect that it is unsafe for full power cartridges, I would insure that it CAN'T be converted back easily, to insure future safe operation at reduced pressure... i.e... epoxy the 22lr parts in place.