So I have a pretty rough Franchi 500 12ga that was more or less free to me.  It has a 28" very light barrel with fixed full choke.  I have no use for this shotgun as is but would love it to be Improved or Modified choke to be a more useful all around gun.  I have looked and replacement barrels are unobtanium. Also being a very light barrel, there is not enough meat to cut and thread for chokes.

My idea is to shorten the barrel until I reach a bore measuring .697~ which should take me to somewhere between Improved and Modified and reset the bead.  Currently the bore measures .675".  I posses the skills to do this and tools but will the shortened "choke" not perform or is this idea plain retarded.  This shotgun has been sitting in my safe for over a year more or less unused so this could also just become an ongoing project.

Any ideas, suggestions, insights would be greatly appreciated.

If the barrel is 'light' you may never get where you want. Just have it reworked for a removable choke.

That would be the ideal situation, but I've been told the barrel is not thick enough to thread for aftermarket chokes.

I bought a rough 870 with a PolyChoke for $150 some years ago, barrel length is 23".
I have no interest in selling it or cutting it down.
Ugly kinda but functional.

^ This....what is the OD of the barrel at the muzzle?

I just measured the OD of the bore at .810".

If the OD of the barrel is .810” (and does not get smaller behind the the muzzle) then its likely you can have Tru-Choke Small Diameter (aka Thinwall) tube installed in that barrel. These tubes are generally rated for lead shot target velocity loads (no steel, slugs, etc). You can message me for more info if needed.

Thank you for the heads up.