Once more Friday is upon us and unless you’ve done something really stupid, you’ve successfully navigated through another week. To celebrate that success, our weekly shoot-the-shit topics allow you to make unsupported statements, use profanity, insult anyone you wish or change subjects altogether! Normally this would run you hundreds of dollars from a licensed psychologist, psychiatrist or philosopher but we now these professionals (Ha! Ha! Ha!) are no more than ambulatory proof that free market economies produce sufficient surplus to support their ass, and for that reason you’ll never see a bill from us. So, without further a do, let’s leap right into our shoot-the-shit topic of the week – Relationship Between Muzzle Blast And Ballistic Crack.
Muzzle blast, is a sound wave propagating 360° from the weapon’s muzzle as high pressure gases in the bore are uncorked by the escaping bullet. Ballistic Crack is the sound wave created by the bullet traveling faster than Mach 1.
Suppressed weapons can be fired with subsonic ammunition or supersonic ammunition. In applications were it is desirable to eliminate ballistic crack we use subsonic ammunition. In making that decision we sacrifice range, and compensate for a loss in kinetic energy by utilizing a heavier projectile. When our target is at a longer range or it’s not possible to close range to the target and still maintain stealth, we use supersonic ammunition. A supersonic round preserves the effective range performance of the caliber but its flight to the target will generate an audible ballistic crack.
There’s an interesting relationship between muzzle blast and ballistic crack, muzzle blast leads ballistic crack; in fact, muzzle blast overruns the exiting projectile within its first 2 feet of flight. At this point, the muzzle blast wave slows and subsides. The ballistic crack wave is characteristically different from muzzle blast in that it propagates as a cone. At muzzle velocities that cone is approximately 130° decreasing to 0 ° as the bullet approaches Mach 1 or 1116 feet per second. As that cone decreases so does our ability to hear ballistic crack downrange. M118LR for example will reach Mach 1 at approximately 985 meters.
Sound suppressors are designed to eliminate muzzle blast and flash signature; however, when used with supersonic ammunition you can expect some degree of exposure from ballistic crack. The effect of ballistic crack is diminishing with range and appears to be limited to a maximum of 130° which is at the muzzle.
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Have an Outstanding Labor Day weekend, be safe, get out to the range or do something fun with your buds and family!