Here is a good article from a guy who test fired one. Click on the link for the story and other pictures referenced in the article. I highlighted his comment on muzzle velocity about 2/3 of the way down.
Bushmaster Carbon 15 Lightweight 5.56mm Pistol
by Jeff Quinn
During the past several years, Bushmaster Firearms in Windham, Maine has become the foremost producer of AR-15 type rifles for the civilian market. They produce a seemingly endless variety of high quality weapons for individuals and law enforcement. Starting as a supplier of parts and accessories for AR-15 and other type rifles, Bushmaster has risen to the top of the heap, producing many more AR-15 type rifles than their nearest competitor.
Now, Bushmaster has begun manufacturing the unique Carbon 15 series of rifles and pistols at their facility in Arizona. The Carbon 15 firearms feature a reinforced polymer upper and lower receiver, along with high quality stainless barrels. They are gas operated like other Bushmaster firearms, and come supplied with one ten-round magazine, but will use any AR-15/M16 magazine. Many of the internal parts are common with standard AR-15 rifles. The Carbon 15 series is chambered for the 5.56mm NATO cartridge, and will use the .223 Remington cartridge interchangeably.
We recently received the Type 97 Carbon 15 pistol for testing. The type 97 features a seven and one-quarter inch fluted stainless barrel that has a unique detachable muzzle brake. Sliding a spring loaded collar forward releases the brake for simple removal, without tools, and it pops right back on just as easily. While the 5.56mm cartridge has very little recoil already, the muzzle brake eliminates muzzle rise entirely. The stainless gas tube is covered by a ventilated heat shield that is very effective in protecting the hand from the hot tube during rapid firing of the weapon. The type 97 wears the very comfortable Hogue hard rubber pistol grip. The controls on the weapon will be very familiar to anyone who has used an AR-15 or M16 rifle. The safety positions are clearly and brightly marked. The magazine release is protected from accidental operation, but is readily accessible for quick magazine changes. The bolt locks open on an empty magazine, and has the familiar bolt release on the left side.
The overall length of the Carbon 15 pistol is twenty inches, but the weight is a feathery 46 ounces. That is lighter than a Ruger Super Blackhawk or a Smith & Wesson Classic .44 Magnum revolver. The Type 97 has a windage adjustable rear ghost ring sight with a ramped post front. The upper receiver is grooved to accept a special Picatinny scope mount base that securely attaches with one screw, and still allows the use of the open sights. Bushmaster also sells mounts to attach a flashlight or laser sight to the grooved barrel of the Type 97 pistol.
I was at first a bit apprehensive about firing the Carbon 15 pistol, thinking that the noise of shooting 5.56mm ammo in a gun with a seven and one-quarter inch barrel would be horrendous. As it turned out, the noise wasn’t bad at all wearing standard shooting muffs. I fired several types of 5.56mm and .223 ammo through the pistol for testing both functioning and accuracy. The intrinsic accuracy of the little AR is as good as any good rifle, but with the short barrel it is not meant to be a benchrest gun. I did not mount a large scope on the little gun as that would have been foolish, and not in keeping with the purpose of the compact and lightweight firearm, instead choosing to mount the excellent Trijicon Reflex dot sight. The Reflex is durable, accurate, and lightweight, and is perfectly suited to the Carbon 15 pistol. Reliability with all of the types of ammunition was flawless in the Type 97. Every round fed, fired, and ejected perfectly. The C15 ejected the empty brass to the right and rear of the shooter, without any damage to the cases. Many short barreled AR type weapons have reliability problems, but the Carbon 15 worked without a hitch, every time. The muzzle brake totally eliminated muzzle rise during firing, making it very easy to rapidly make multiple hits on the target. I really like the detachable feature of the muzzle brake. The design would make it easy to attach a flash hider or sound suppressor to the muzzle, should a shooter choose to legally obtain either.
This would be as good a place as any to discuss the purpose of the short little AR. There are places where this pistol would prove to be much handier than a rifle, such as in the confines of an automobile or a cramped hallway. For a police entry team, the Carbon 15 would be very maneuverable, while still carrying thirty rounds of 5.56mm firepower. Out of the short barrel, military ball and hollow point ammo has a velocity of over seventeen hundred feet per second,
and has virtually no recoil. Rapid fire repeat hits are easy. Muzzle flash from the short barrel is bright, as can be seen in the accompanying photo, but a good flash hider would take care of that for those who need one.
There is also another place where this pistol excels, and it became apparent to me during the testing of the Carbon 15. Without a doubt, this pistol is one of the most downright fun guns to shoot that I have ever tried. Loading a GI surplus magazine with thirty rounds of ball ammo and blasting away at rocks and steel plates is, for some reason, extremely enjoyable! The lack of recoil and bright muzzle flash in rapid fire is a real hoot, and has to be experienced to be fully appreciated. There are times when a gun means the difference between life and death, and the Carbon 15 can fulfill that role if needed. There are also times when shooting should be relaxing and entertaining, without thinking about tactical drills and exercises. This pistol is very entertaining, for the shooter and observer alike. It is lightweight, handy, reliable, and just plain fun.
"People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf." ---George Orwell