Developed a wildcat for the M1 Carbine using .30 cal Blackout shortened to 1.220 case length. Used NATO 556 for parent case. Allows a higher ballistic coefficient bullet (~0.293, 110 grn). Velcity ~2000 fps, energy ~975 ft.-lb. Ballistic calcs show 9mm muzzle velocity at 380 yds. The cases are very easy to make. Cycle fine. Another development - M1 Carbine in 256 Win Mag Rimless (also based on 5.56 NATO parent case.) Velocity~ 2400 (75 gr bullet), or 2230 (85 gr). Used a 5.7mm Johnson for the barrel. Very accurate (for a carbine) - ~1.5-2 MoA. Ballistic coefficient still around 0.3. Also a 400 yd round (using the 9mm MV as a metric). Cases are a little harder to produce than the Short BlkOut cases. Maybe some overpressure signs with standard propellant. Have used AA1680 to reduce pressure.