what exactly the difference is between vent rib, solid rib, and no rib?

If I'm not mistaken it is the part of the barrel that rises to creat a flat surface. Usually the shotgun sites are mounted on it. A vented rib I believe has slots cut into it so that it isn't solid. Then the no rib would be a perfectly round barrel with no flat point.

Tom

A ventilated rib has lateral openings that will allow more air to circulate to increase the rate of cooling the barrel, and to minimize any distortion of the sight picture from heat waves.

A solid rib is a barrel/receiver rail that does not have any lateral openings in it. This is known as a box rib.

I found these on the MidwayUSA’s website. They have a Gun-Tec Library on their site that really helps. I hope these answers the questions you had.

Statjunk is correct in his basic description of a barrel rib. It's intent is to give the shooter a flat plane to look or sight dowm, instead of looking at a drop and percepted rise in the appearance of the barrel when aiming. The ventilated rib is usually set on individual posts soldered to the barrel, and then the flat rib itself is attached to these posts. A solid rib is just that....a solid raised rib on the barrel with no airspace underneath it. No rib is simply a plain barrel. Hope this helps................