BAC
04-29-09, 12:21
To preface, this is mostly caliber-independent. I have no particular calibers in mind when bringing this up, though some may prove more consequential to the discussion than others.
Question: Is there a minimum threshold, in terms of bullet construction, depth of penetration, impact energy, size (density might fall under this or construction), and velocity, that a round must possess to reliably perform out of a precision rifle against light barriers like windows and thin walls?
Reading Dr. Roberts' stickied topic on LE .308 Sniper Loads, there is a clear divide between the ability of .223/5.56N rounds and 6.8/.308/7.62N rounds in penetrating barriers while still providing acceptable terminal performance. My first instinct is to say that the larger bullets simply have more "stuff" to work with. For depth of penetration, At least with Hornady TAP rounds, all rounds seemed to offer at least 12-13" of penetration, most hovering closer to 15". In terms of size, the .308/7.62N is pushing a bullet two or three times as large as a .223/5.56N. A 6.8 looks to be pushing a bullet about twice the size of a .223/5.56N. For velocity, the gamut is run between high 2400s and low 2800s, for all rounds presented (.223/5.56N seem to run nearer the higher end, 6.8 nearer the lower end, .308/7.62N somewhere in the middle). Obviously energy is going to favor the larger rounds, though I don't have or know of any numbers to quantify this more clearly. Just simple physics talkin'.
But say some enterprising LE agency wanted to say "to hell with .223 and .308 for sniper use," what might be some good guidelines for acceptable penetration? There are a variety of 6-7mm bullets out there that are fantastic for accuracy and have been downing game effectively for decades, so I imagine something in this range must qualify for that happy medium between the too-small .223/5.56N and the can-be-improved-upon .308/7.62N.
-B
Question: Is there a minimum threshold, in terms of bullet construction, depth of penetration, impact energy, size (density might fall under this or construction), and velocity, that a round must possess to reliably perform out of a precision rifle against light barriers like windows and thin walls?
Reading Dr. Roberts' stickied topic on LE .308 Sniper Loads, there is a clear divide between the ability of .223/5.56N rounds and 6.8/.308/7.62N rounds in penetrating barriers while still providing acceptable terminal performance. My first instinct is to say that the larger bullets simply have more "stuff" to work with. For depth of penetration, At least with Hornady TAP rounds, all rounds seemed to offer at least 12-13" of penetration, most hovering closer to 15". In terms of size, the .308/7.62N is pushing a bullet two or three times as large as a .223/5.56N. A 6.8 looks to be pushing a bullet about twice the size of a .223/5.56N. For velocity, the gamut is run between high 2400s and low 2800s, for all rounds presented (.223/5.56N seem to run nearer the higher end, 6.8 nearer the lower end, .308/7.62N somewhere in the middle). Obviously energy is going to favor the larger rounds, though I don't have or know of any numbers to quantify this more clearly. Just simple physics talkin'.
But say some enterprising LE agency wanted to say "to hell with .223 and .308 for sniper use," what might be some good guidelines for acceptable penetration? There are a variety of 6-7mm bullets out there that are fantastic for accuracy and have been downing game effectively for decades, so I imagine something in this range must qualify for that happy medium between the too-small .223/5.56N and the can-be-improved-upon .308/7.62N.
-B