Odd that Midway would list the 150gn job for 7.62 x 39.

Most bullets for that cartridge run 124 to 130gn to achieve working muzzle velocity and port pressure.

If they have a stock of 150gn .310 (ish) bullets at the "right price", grab a swag and play with them. If you are not entirely satisfied, you can easily off-load them to folks shooting 7.62 x 54R, .303, 7.65 Argy / Belgian, 7.7Jap etc.