I've settled on a 7.62x39 AR pistol upper from PWS for my next build. I'm looking for it to be both a range plinker and home defense gun. The MK107 (7.75" barrel) looks awesome but I don't know  if its to short for the x39 round to be anything other than a fire breathing range toy. PWS advertises a muzzle velocity to be 1944 f/s. Is this enough speed for x39 to be effective terminally?

Or should I just opt for the MK111 where they advertise a muzzle velocity of 2204 f/s?

Thanks in advance guys!

1944fps is close to what I have seen with an 8" 7.62x39 ar @ 2025 fps with wolf.

Many of the hollow point, soft point and polymer tipped projectiles have a minimum expansion velocity between 1600 fps and 1800 fps.

At a muzzle velocity of 2000 fps (nice round number), and a G1 BC of .270 (based on m43). 1800 fps is reached @ ~70 yds and 1600 fps is reached @ ~150 yds.

Most FMJ in 7.62x39 tumbles and can exhibit tumbling below velocities of 1600 fps.  You would need to select a particular round to determine if tumble based wounds are appropriate for your need.

Additionally, there are several .308" diameter bullets with much lower expansion velocity thresholds, designed for use in 300blk. Most 7.62x39 barrels are between .309" and .312" and as a result .308" may or may not be suitable for your particular barrel, but that is something you will need to decide.

Personally I would not have an issue with a 7.75" barreled 7.62x39 out to 150 yards.

This is exactly what I needed to hear. Much appreciated friend!