Am I reading this wrong, or does the carbine-length barrel not add much to velocity?
http://www.ballisticsbytheinch.com/9luger.html
Really depends on the bullet weight. Shooting the heavier 9mm bullets, you just can't load them that hot (and remain safe) so longer barrel just gives more friction resistance---you don't gain much at all.
Lighter rounds, on the other hand, can get kicked up quite a bit. Through my 16" barrel, my USPSA loads (125gr Blue Bullets, 4.7gr WSF, 1.12 OAL) chrono averaging at 1310 ft/sec, when they run more like 1085 in my G34.
115s loaded hot would show even more of an increase.
It looks like roughly a 20% increase in velocity with the longer barrel (which varies from one load to another). Is that a significant increase? There has been a big debate over whether there is a practical difference between say 9mm and .40 caliber. So is the increase in power from the longer barrel enough to affect stopping power?
According to literally all of the current research, there is no functional difference in effectiveness between a 9mm, .40, and .45acp, given modern JHP loads in each, against a human target.
Psychological stops on human attackers have nothing to do with actual damage done, and caliber plays no part in that. Physiological stops on human attackers, at pistol velocities, require direct hits to CNS or hits to the blood pumping system and tons of time---and in those cases, there just isn't any functional difference in the effectiveness of the three standard "defensive" calibers.
An increase or 200-300 ft/sec still doesn't get anywhere near rifle velocities, and I'd expect there to be very little functional difference with that, OTHER than 1) dealing with intermediate barriers, whereupon it will depend on the velocity envelope of the bullet design as to whether or not it helps or hurts, and 2) decreased trajectory changes based on distance (which is normal with higher velocities obviously).
There are reasons beyond increased power to have a pistol caliber carbine, like greater accuracy, and I expect to be buying one.
One of the interesting things that seems to be becoming very noticeable in USPSA matches is that a lot of the quick movement, angles, and ports, are showing that pistols are much easier to be fast and accurate with. (This shouldn't be a surprise, but many people were touting how handy and fast SBR-ed pistol carbines would be.) For 25+ yard targets (especially distant steel), PCC seems to be showing strong even against Open pistols, but for shorter-range stuff (particularly in and out of ports) it is interesting to watch how difficult people are finding it.
