Monday, August 8, 2016

Birdshot is for the birds


This is a post I made on a gun discussion board; I have reposted it here. The question was whether birdshot was a good choice for self-defense. My answer has evolved from some years ago, when I  said that size T lead shot (.20 caliber; #4 buck is .24) could be ideal. I even said something positive about Federal Cartridge's attempt (since abandoned) to offer even smaller shot in a defense load. But I now conclude that #4 buck is the sensible lower limit of shot size for self-defense use, and it is a case where theory and practice bear one another out.

#4 buck is already on the ragged edge where performance is starting to falter occasionally, in circumstances where the distance is a little bit far or there are heavy clothes or light obstructions involved, and that lines up closely with what you would expect if the military estimate of wounding energy were true, or else close to the mark.

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 Yesterday, 05:37 PM  #12
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It is an old military rule of thumb that projectiles need, at the least, 58 foot pounds of energy to produce a killing or disabling wound, reliably. That idea was cooked up in relation to designing and using old fashioned Shrapnel shells, later applied to artillery fragments and was most recently used in the design of the Claymore mine. It's not very exact, for people have been disabled or killed by far less energetic projectiles, but general rules are just that: they have exceptions.

Unless the calculator I used is way off, #4 buckshot launched at 1250 fps is down to 58 foot pounds just nine yards from the muzzle. (For comparison, #1 buckshot launched at the same speed has dropped to 58 foot pounds of energy when it has flown 76 yards and 00 buck gets out to a trifle more than 115 yards before its energy drops to that level.)

We know anecdotally that #4 buck works farther than nine yards, but we also know its reputation for poor performance as distance increases. We have read of police becoming disgruntled with the load and switching to 00, due to indecisive results when suspects were hit with #4 buck. At other times it has worked quite well, and its good pattern density is obviously an advantage in getting hits on the target.

We are flirting with the limits of ineffectiveness with #4 buck, and the results show it. That seems to bear out the military's 58 foot pounds estimate, and suggests to me that #4 buck is a sensible lower limit.

   
  

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