Sleeving up a gauge

[Ed Blake]

If the frame is large enough to accommodate the bigger gauge, then sure it can be done. There are a number of Parker 10/12 two barrel sets on both the 2 and 3 frames. Could you see the sleeping line at the end of the chamber?

[Milton Starr]

I'm not familiar with sleeping lines I didn't handle the gun it was on a antique gun website in the U.k. . I know a gunsmith who bored non taper 10 gauge barrels to 8 gauge and tested them to 21,000 psi but that was modern steel .
ive seen purpose built guns like 16 ga on 20 ga frame or similar but never a frame built for one gauge having a larger gauge built on it .