Is there any appreciable benefit to running a longer, protruding barrel? Is there an increase in accuracy or muzzle velocity?

Since Gen5 Glocks have the same barrel lock up now, you could conceivably run a G34 barrel in a G26. Ridiculous, I know, but I was thinking more about dropping a G17 barrel in a G19.

The only (usually) assured benefit to a longer barrel is higher muzzle velocity. To cite just one example of my own, from a 4.4 inch P226 barrel Winchester Q4318 (124 grain NATO) averaged 1130 fps; from a threaded 4.9" barrel the average velocity was 1170 fps.

Longer barrels do not automatically improve accuracy; the opposite is in fact sometimes true, although such variables are more likely to be factors in rifles than handguns.

The accuracy gains that are common in longer barreled revolvers 0ver their shorter tubed brethren are not due to the length of the barrel, they are due to the longer sight radius

In the olden days of bullseye it was common to see firearms with extended front sights in order to gain an accuracy advantage



As sigfreund demonstrates, a loner barrel by itself will usually only yield a velocity increase

I run a threaded barrel but that's about as far as I'll extend out the front of the slide. Velocity is the only benefit I can think of but you trade handling and can probably knock it out of battery easier.