NYPD made out pretty well with .30M1 Carbine soft point loads, according to what I've read from Jim Cirillo, and comments from Pat Rogers. I'd still prefer M193 Ball, but would not feel too bad about using a carbine in good condition with SP loads at short range.
Richard, you are essentially describing the 6.8mm Rem SPC cartridge, which Remington has launching 115 grain bullets at a nominal 2800 fps. Complete uppers, parts kits and barrels in this caliber are already being sold by Model-1 Sales (and soon by others, I'm sure). Remington is cataloging several loads in 2004, and Midway expects to start shipping it shortly. I think Robinson Arms also has carbines in this caliber on the market. So what you want is a reality, or will be soon, when the ammo makes it to dealers.
Richard, you are essentially describing the 6.8mm Rem SPC cartridge, which Remington has launching 115 grain bullets at a nominal 2800 fps. Complete uppers, parts kits and barrels in this caliber are already being sold by Model-1 Sales (and soon by others, I'm sure). Remington is cataloging several loads in 2004, and Midway expects to start shipping it shortly. I think Robinson Arms also has carbines in this caliber on the market. So what you want is a reality, or will be soon, when the ammo makes it to dealers.