What everyone said it basically true.. but the ability to be wrong is high.. Perazzi has made several different barrels..with different bore sizes.. and shooters have helped the confusion along well.. While the # is based on the original bore size.. whatever it might be.. the actual choke is the difference between the bore diameter and choke diameter.. For instance.. You have a barrel that measures .732.. Your choketube measures .710.. That gives you a .022 choke... Put the same tube in a .724 barrel..minus the .710 and you have a .014 choke.. vastly different.. despite what the numbers say.. A bore gauge does not lie.. and has no friends..
I also caution shooters about using some of the older chokes in newer barrels.. If the skirt is exposed..and a wad can catch on them..you'll blow your tubes out of the barrel.. On the old MT-6.. often the barrels were backbored..and choketubes properly fitted.. Then after an owner or two down the line...unaltered choketubes were tried that were not modified for the larger bore.. Many a blown choke section was the results.. Hope everyone enjoys today.. All Good Mike