There is a practical purpose. First, self defense. The shorter barrels offer plenty of ballistic power - rifle power - which is much higher than most pistols. Since the barrel is so much shorter it then offers more maneuverability in urban construction and exiting from vehicles. This is why the DOD moved from 20" to 14.5", and why smaller special units use the 10.5" Mk18. Shipboarding and urban townhouse assault, for example. The Army has been using 10.5" barreled AR's since the 1960's - It's now a 50 year old concept and well proven. So, sorry if some haven't got the memo. As for 7.5", 5.56 isn't optimal. Go .300BO or 6.8SPC and the ballistics step up significantly, but the ammo costs don't go down for practice. That's why so many stick with 5.56. In civilian life, what happens on a range might be one users toy, but hunters are another matter. In MO, the AR pistol is - a pistol. It can be used in rifle season as well as it's own Alternative season, for a total of 4 weeks. A 10.5" barreled pistol can be expected to have 1,000 foot pounds well beyond 125m - which is a common limit to hunting whitetails in broken Ozark woodlands. Using 77 gran OTM or TMK, there is plenty of ethical power and range, plus the advantage of light weight and a significant reduction in weapon length while trying to move quietlyn thru dense underbrush - where I've staked out a hotspot for deer laying up after leaf fall. I could take the 6.8 again, but building another AR needed a purpose - another reason for the shorter barreled pistols. And as a reminder, some of us build them because they are legal. Complaints about that are just disarmament fodder for antigunners. I don't need anyone's permission to do what is my right. As for the muzzle blast, there are things like electronic muffs, silencers, and ear plugs. An AR pistol with linear brake is no worse than a 16" AR with side exiting muzzle brake - and in most cases, a lot better. One shooter took his to a carbine course over a weekend, shot over a thousand rounds on the line with RO's in close proximity, and when he asked "does the blast bother you?" he kept getting quizzical looks. They didn't get the point of the question. It wasn't as bad as the compensators and brakes we've seen marketed that run the guys in the next lane off. As for accuracy and range, they have been known in the hands of decent shooters to hit targets out to 400m - with lethal results on humans. All this, of course, is documented on the internet, which is where I found it over the last three years. If the first someone bumps up against it is loud noisy shortbarrels deliberately built to make noise on the range, I'm going to suggest you are only seeing those who built a range gun. Those with more serious intent know how to configure them properly and when and where they are used - not on a sunny Saturday afternoon showing off to their buddies and all.