A 10 inch swing will probably be enough providing that the spindle bore is large enough.
I have a 10x21 import lathe that I can easily and consistently turn precision work on, you just have to take into account the limitations of the machine. On a big, heavy, expensive lathe you can turn to a diameter in far fewer passes, on my little import I have to sneak up on sizes with roughing and finishing cuts. I can chamber, thread shanks and barrrels, (no bull barrels).
The best upgrade I have done to my lathe was switching over to a larger 3 phase motor and a VFD, being able to turn the work at the proper speed is a big plus IMO.
NRA Lifetime Member Since 1999
"I ask, sir, what is the militia? It is the whole people except for a few public officials." George Mason