Part 3: Variant
Bullet Variations:
In addition to the different types of cartridges defined by their bullet diameter and casting height, there are variants within each type defined by weight and fill.
Weight:
Each cartridge type (.22 cal, .380 ACP, 9mm, .40 cal, and .45 ACP) has a weight range. As an example you can purchase 9mm in 115, 124 or 147 grains. This measures the weight of the bullet (not the entire cartridge). A grain is a united of measure that is 1/7000 of a pound. It is generally accepted that heavier bullets have greater energy transfer and create larger shockwaves, which increases the effectiveness of hydrostatic shock.
Fill:
Some cartridges are labeled with “+P” or “+P+”.
“+P” = extra pressure
“+P+” = ultra high pressure.
These cartridges use special powder that provides more force to propel there bullets. These types of cartridges should only be used in firearms that were designed for them. The higher pressure allows the bullet to be propelled forward at a faster rate. Based on our earlier equation ( F = Max times acceleration) a faster bullet leads to more force.
FMJ vs HMJ:
In regards to civilian pistol cartridges there is another class of variation.
FMJ = Full Metal Jacket
JHP = Jacketed Hollow Points
FMJ and JHP describe the shape of the bullet. FMJs are your classic dome (round) tipped bullet. JHPs have a cavity cut out of the middle (See attached picture .40cal JHP 180 grain).
FMJs retain most of there shape upon impact but will deform when they hit a solid object. The aerodynamic shape of FMJ allows them to travel faster and with more accuracy than JHP(note because of the close quarter nature of defense situations the aerodynamic shape may be negligible because all modern bullets are relatively accurate at close range). Since FMJ don’t deform in soft tissue, as found in living targets, there aerodynamic shape allows them to penetrate deeper into a target. If enough force is applied sometimes over penetration occurs and the bullet exits the target. The greatest danger in over penetration is the bullet may still have enough power after exiting to injury an unintended target. Other affects of over penetration are decreased energy transfer and decrease the effect of hydrostatic shock.
JHPs are designed to deform upon any impact. The deformation is engineered so the bullet “blossoms like a flower”. This blossoming increases the bullets surface area preventing over penetration and allowing the bullet to transfer nearly all its energy into a target. This result in greater energy transfers and increases effects of hydrostatic shock.
Studies of JHP have been done on ballistic gel and much debate surrounds the effectiveness of JHP. Critics of JHP show that when JHP are fired at cloths wearing targets the fabric from their cloths fills the cavity of the JHP causing it to behave similar to a FMJ. JHP technology has improved greatly and claims have been made that this is no longer an issue. Supporters have JHP have also suggest that according to the study mentioned above a JHP that behaves similar to a FMJ is still as affective as a FMJ therefore JHP are still superior for self defense.
Stay tuned for part four: Generally Accepted Information and my works cited page.
Table of Contents:
Part 1: Components and Naming (12/11/09)
Part 2: Stopping Power, Energy Transfer, Hydrostatic Shock (12/11/09)
Part 3: Weight and Fill (12/15/09)
Part 4: Generally Accepted Information (12/15/09)
