Invector plus choke tube in different shotgun

[Bugflipper]

I have an old savage 775 which has been chopped down a bit and an invector plus thread put in.
A standard 12ga bore is .729. An inv+ is .742. I am assuming an inv+ is over bored like the 835 mossberg? This is a 1948 shotgun it is on so I am guessing just a standard .729 bore with a big choke in the end. I was going to use it for bobwhite, but I don't want to have to stand on top of them to get a shot. Right now it has an xx-full in it so no good for me. I wanted right around a modified choke for a 30-35 yard pattern on it. Which one would get me there?
Thanks

[spruce]

It's anyone's guess without patterning it, but I would try the Invector Plus "full" tube - looks to be about the closest in size to the standard modified choke.
 
Curious - have you patterened the xxfull tube yet?

[Bugflipper]

I haven't patterned it. The receiver is much higher than the plain barrel. I am going to try to find a ramp for the bead to get the aiming point up. Right now it doesn't even have a bead, but there is a hole for one. I really can't understand why they would have tapped it for the inv+. My way of thinking on the diameter was the same as yours, but I was unsure so thought it best to ask for advise. I appreciate it.

[spruce]

Just a guess really - basing it on the fact that choke looks to have about the right amount of constriction according to the numbers on the chart.  No way to tell how your particular barrel/choke combination will actually pattern without trying it.
 
Hate to see you waste your money based on my free advice!!!

[Bugflipper]

Not a problem. The last time I owned this shotgun it had an x full choke and had a good pattern for hunting at 40-45 yards. I never patterned it to paper though. I think I will just get a full and modified. That should be good for thick and open woods. This was my first shotgun. I spotted it in a pawn shop 10 or so years ago and picked it up again. The quail population took a nose dive so I never really had any use for it. Now the population is back up and it's time to take the chessy out to earn it's keep.