I'm thinking of either a Glock 26 or 27 for CCW.  I currently have a G30 but would like something a little smaller.  I've been told that in .45 you should try to have at least 4.5" of barrel to take advantage of the ballistics of the round. (I've also been told that Glock's rifling makes up for this in the G30)  

My question is what is the minimum barrel lenght to obtain good results witht the 9mm and .40 rounds?  Are the baby glocks too short in the barrel to take advantage of these rounds?
Please give me some insight.
Thanks.

There's no real way of giving you an absolute answert due to the different designs & idiosyncrasies of all the different bullet types.

Federal, Remington, etc., all perform differently when used in slower or shorter barrelled guns.

There are some general rule of thumb rules, IMO. Generally speaking, one loses 50/fps per inch of barrel loss below 4". So going from a 4" S&W to a snubbie would usually cost you 100/fps.

There's also some variations such as using +P ammo to make up for some loss but again, you may have some bullet design influences.

Glock & H&K also kinda through off the usual loss of velocity due to their different rifling design.

You can always get a Glock 26 or 27 & then shoot 3-4 water jugs in a row & see how well or little it expands. So you don't have to buy an entire box of ammo just have a buddy give you one or two rds of whatever he uses.

Some have maintained that for these super short barreled guns it might be best to stick with FMJ. They say that the loss of velocity drops overpenetration worries to almost nil.

There may be some brands who make specific bullet types for short barrels but I don't know of any.

My .o2

Thanks for the info.  

Between the 9mm and the .40, does anyone know which performs better out of a short barrel?  Lets say 3.5"?
I think that I remember hearing that the .40 requires at least 4" of barrel to expand but I can't remember for sure.

Either out of a  half inch barrel is still better then a sharp stick in the eye.

  I would go with the 9. But the reason I would pick it is because the 9 is a lot easier to control and that's what really counts, just my opinion.
  As for the glock, heh, that's your opinion.