According to the JBM Ballistics calculator, a 122gr 7.62x39mm JHP (ballistic coefficient 0.2607) fired at an angle of 30 degrees above the horizon will come down 3260.0 yds away. That's over 1.8 miles. Impact will occur nearly 24 seconds (!) after the shot is fired. If you live well above sea level or are using heavier bullets, it would likely go further than that.
When it comes down, it will be descending very steeply (62 degrees) and traveling 350 ft/sec, meaning it could still inflict a fatal wound to an animal, child, or adult if they were standing out in the open and were unlucky enough to get hit with the negligently fired round.
Your uncle is flat wrong, and I sure as heck hope that there isn't any occupied territory downrange.
The only way his advice could be construed as possibly making any sense whatsoever is if someone once told him that about shooting a shotgun with birdshot while hunting, and he doesn't know enough to know that that advice would apply ONLY to shotguns using birdshot.
http://www.eskimo.com/~jbm/calculations/calculations.html
JBM Maximum Distance Output
Input Data
Ballistic Coefficient: 0.261 G1
Bullet Weight: 123.00 gr
Muzzle Velocity: 2350.0 ft/s
Temperature: 59.00 °F
Pressure: 29.92 in Hg
Humidity: 0.0 %
Altitude: 0 ft
Std. Atmosphere at Altitude: No
Corrected Pressure: Yes
Calculated Parameters
Atmospheric Density: 0.07647 lbs/ft³
Speed of Sound: 1116.5 ft/s
Initial Angle: 30.0 deg
Terminal Angle: 62.3 deg
Terminal Range: 3260.0 yds
Terminal Velocity: 350.2 ft/s
Terminal Time: 23.989 s
Terminal Energy: 33.5 ft•lbs
That is about the strangest, dumbest thing I ever heard. Good on 'ya for not doing it.
