OK, it seem apparent that there is a correlation, but how much one is there.  For example what kind of difference would there be between a 4 inch barrel and a 6 inch one?  I read a review of the Glock 17L (six inch barrel) that claimed to get 1500 fps from corbon 115 +P.  

I'm trying to decide if my next should be a g19 or g17L.  Yes, I know there are other factors, but I'm just trying to examine the muzzle velocity angle here.

thanks

anyone?

usually, the longer the bbl (with in reason) will provide more velocity as it allows the cartrige to burn most of the powder while keeping the bullet stabalized for maximum velocity/optimum stability

h/w, too long of a bbl and you begin to loose velocity as the bullet will start to drag and the powder is gone

there are other factors too, like the propelant and how fast it burns--faster burning powders will get better velocity from shorter bbl guns than regular poweder

usually, a bullet will loose 50-75fps for every 1in less of bbl from the usual lenghts (20in AR/M1A, 5vs4vs3in 1911s, etc)

i would get teh G19--best all around 9mm glock and the 4in bbl still provides near optimum velocity in a HG; h/w, if you were to shoot the same 9mm in a longer length bbl (~12in), you will get a lot more velociy--near maximum as all of the powder is burned, but past ~12in, the 9mm will begin to slow down

i'm pretty sure thats how it works, someone correct me if not, thanks

The loss in MV from a G17 to a G19 is not much, and not enough to matter.

Wil Schuemann states that most of the attained velocity occurrs in the 1st inch of rifling.

Thanks guys.  That does help some.  So it seems that you guys don't think there's much velocity increase between a 4 and 6 inch.

I don't know who Wil is so I would hate to disagree with a mystery expert and then be proved wrong.  However the data I have seen states that a 14.5" barrel on an AR15 generates less velocity than a 20" inch barrel, which agrees with my general understanding that the same is true for all guns.  In general, the longer the barrel the greater the velocity generated by the gas from the "explosion".

It is difficult to illustrate this from most balistic tables since they generally give the various data using one barrel length.  However in the linked table, I found one entry using the same bullet with two different barrel lengths (2" vs 4").  The shorter barrel generated 206'/sec less velocity when using a 158gr Winchester +P round.  Not totally insignificant to some, I guess.  

I also found this quote comparing the Glock 22 and 23, but can't confirm it's accuracy.

"The amount of velocity lost when you opt for the Model 23 is minimal (no more than 4%) as its barrel is less than a half-inch shorter that the Model 22's tube. There is no practical effect whatever on the wound ballistics potential. I prefer the Model 23 as it can be concealed more easily."

http://www.chuckhawks.com/handgun_power_chart.htm

i'm not sure, but i THINK that +p/+p+ ammo will get you pretty much the same velocity in a std. size bbl and a little shorter bbl b/c the faster/hotter burning poweder will burn out faster....

The general rule of thumb which is also consistant with my experiences is that there will be a velocity loss of from 25fps to 45fps for every inch of barrel removed.  This is not a hard and fast rule.  Certain cartidges, particularly small volume, high pressure cartridges like the 9mm Parabellum are noticably less sensitive to barrel length.  The 9mm works almost exactly the same in 4" barrels vs 5" barrels and there isn't a big loss even in 3.5" barrels.  Interestingly, a similar situation seems to occur with the .45ACP which is a low pressure cartridge (small case volume, though).
As has already been stated, all of this can vary with the propellent used in the cartridge.  There is a significant range of variation in my 20" AR vs my 16" AR depending upon powder selection, with a 37fps per inch (4 x 37fps = 148fps) loss in 16" from 20" being the average with my particular rifle barrels.