I’m looking at a few new and used guns and it appears that kolar went to a different diameter barrel (0.740) in the latest 3rd gen gun. Functionally, are there any other differences that I should be aware of and is the newest barrel/gun that much different?

If I understand it correctly (and it's very possible I do not) the first generation barrels were .740", second generation barrels were .750", and then the third generation went back to .740".

Having said that the current .740" configuration is a much lighter gun than the first generation was.

There's some .735's in there, somewhere. One of the fellows at our club claims his are .735 and I've seen a couple listed on Gunbroker in the past that claimed .735 bore.

The 735s were the 12ga barrel mated to a carrier barrel with subgauge tubes. I'm sure you could order a gun with just 735s, but almost all of them would have come as part of a 2 barrel set. They use 740 bore pattern chokes, your choke will just have .005 constriction less than marked.

The current gen 740 barrels also have a lightened monoblock which shaves a tiny bit of weight as well.

Thanks for the info. All things being equal, are there any pros/cons to buying a 735 vs. newer 740 gun?

There is no reason to seek out a 735 bore gun unless you have the mating carrier barrel to go with it, or MAYBE if you're shooting fiber wads. I don't think Kolar has even offered the 735 bore quite a while.

Mine is a 735 bore carrier combo, but the chokes were designated as 735 bore. Not 740 bore.

I'm sure they are marked 735, but they use the 740 bore thread pattern. 735 marked chokes are pretty hard to come by now that they don't make that bore anymore, so it's good for people to know that the 740s will fit, just be .005 off.