Gunblast article

[LouBoyd]

Since we're talking about the 300 BLK and the tradeoffs of bullet selection for energy versus distance this may be of interest. It's why I'm only interested in the 300 BLK with heavy VLD bullets.

Using rsilvers BC of .338 and a MV of 2216 fps for 125 grain 300 BLK ammo
and a BC of .673 and a MV of 1025 fps* for a 240 grain SMK in a 300 BLK case
Quickload shows the 240 grain subsonic will have more energy beyond 500 yards.

At 520 yards the 240 grain has 41 feet of drop , 1.6 seconds time of flight, about 1.9 " per mph crosswind deflection. and 425 ft-lbs energy.

At 520 yards the 125 grain 300 BLK only has 13.5 feet of drop and 1 second time of flight but it has 4.5" per mph crosswind deflection and 417 ft-lbs energy.

The drop may seem like a lot for the 240 but it's only a function of time of flight and it's repeatable. Wind velocity is difficult to measure (downrange matters too) but the high BC bullet subsonic bullet has less than half the crosswind deflection.

Additionally the 240 from a 16" bolt action with a suppressor will be very quiet.

Of course a 240 SMK can be shot from a 30-06, 300 Win Mag or 300 Norma Mag and get better performance in all categories except quiet and recoil. For quiet and recoil the 300 BLK is a superior cartridge. There are larger subsonic cartridges with better ballistics but none as easy to obtain.

*1025 fps is not the fastest the 240 SMK can be driven by the 300 BLK cartridge. In a bolt action where it's not magazine limited the 240 SMK can be driven to over 1200 fps with Accurate 2460 powder giving over 800 ft-lbs energy. However this will put the bullet at the high end of the transonic range with much higher drag. It would lose the virtue of the 240 BLK of being quiet with a suppressor.