Question for the experts: Expanded Diameter?

[Shawn Dodson]

Duncan MacPherson's bullet shape factor (phi) gives you an idea of the average diameter of a handgun bullet's permanent cavity. I'm in the middle of moving to a new home but IIRC an expanded JHP has a value of 0.69. The permanent cavity produced by a handgun bullet varies in diameter, tapering from larger to smaller as bullet velocity decreases with penetration. In essence the permanet cavity is larger in diameter at the beginning of the wound track because the bullet is penetrating faster than soft tissues can stretch and move out of the oncoming bullet's path. As the bullet's velocity slows it allows soft tissues stretch and move out of the way. This is where bullets with a cutting mechanism, like Winchester Ranger T, provide an advantage as it cuts soft tissues that would normally stretch and flow around the smooth contours of an expanded conventional JHP bullet.

[JHC]

In related matters:

http://www.luckygunner.com/labs/revo...istics-test/8/


Comparing .38 to .357 from a 2" barrel.

[DocGKR]

JHC: https://pistol-forum.com/showthread....221#post587221

[DocGKR]

If we only carried single shot firearms, a larger caliber projectile might be an advantage; with a magazine fed handgun, other factors come into play and a balance between "shootability", magazine capacity, and terminal performance must be made. At this time, most folks are best served with a 9 mm handgun with a minimum 15 rd magazine capacity shooting barrier blind projectiles which meet the FBI specifications of 12-18" penetration while offering robust expansion.

[QED]

Duncan MacPherson's bullet shape factor (phi) gives you an idea of the average diameter of a handgun bullet's permanent cavity. I'm in the middle of moving to a new home but IIRC an expanded JHP has a value of 0.69. The permanent cavity produced by a handgun bullet varies in diameter, tapering from larger to smaller as bullet velocity decreases with penetration. In essence the permanet cavity is larger in diameter at the beginning of the wound track because the bullet is penetrating faster than soft tissues can stretch and move out of the oncoming bullet's path. As the bullet's velocity slows it allows soft tissues stretch and move out of the way. This is where bullets with a cutting mechanism, like Winchester Ranger T, provide an advantage as it cuts soft tissues that would normally stretch and flow around the smooth contours of an expanded conventional JHP bullet.

Round nose has a bullet shape factor (MacPherson's phi) = 0.69; for JHP, phi=0.82, making effective diameter of a JHP within about 10% of the cylinder (wadcutter).

[QED]

Guys,

Just thinking this through. If a round at its maximal penetration depth for arguments sake of 16" is .68" that represents it's terminal state. It's dynamic expansion is actually somewhat larger true? For example as the round expands the petals flare outward as they are "peeled" back to their final resting diameter, thus the wounding tract is actually larger than the percieved ".68" diameter would leave one to believe? Your thoughts are appreciated.


P.S. I have been drinking wine

Dave

Generally, maximum energy transfer, and thus wounding, occurs at the point where the petals of expanding handgun JHP reach maximum expansion; usually within 2 inches after impact with bare gel/soft tissue. However, the petals usually "fold" quickly, and typically after only about 3 inches after impact a handgun JHP loses about 50% of its energy (part of that energy used up to "open up" the JHP).