Hi AnonBob,
Do you have an SB-2 receiver? Those can come from the factory as 10ga and should hold up as long as you follow SAAMI specs.
For some real slug fun, look up Mr. Ed Hubel over on... practically any forum on the net posting as Hubel458. He's a hero when it comes to 12ga, 10ga, 8ga, 4bore, etc. slug and big buckshot loads. He's used the NEF SB-2 receiver to chamber in 8GA FH (what he's dubbed "8ga FROM HELL!")
You can use the SB-2 barrel you have (depending on what it is) and bore it out, internally thread it, then externally thread your 10ga rifled blank. What wall thicknesses would remain if you took that path? Do you have a barrel on the receiver currently, or just a frame and a blank?
jkpq45