Effective Shots From True Pocket Guns

[ revised on Mar 21 ]

Sometimes most shots in a sudden handgun fight are misses, or grazing hits.
Hits might first pass through a heavy coat, bone, or safety glass, sometimes
at shallow angles, before causing effective soft-tissue penetration, which is
more important than expansion, fragmentation, or yaw. [per FBI]
A second effective hit on a perp is often necessary; maybe within 2 seconds;
and likewise for any second perp.  Sometimes you might want to penetrate
laminated auto door glass.  (Windshield penetration is for cops while on duty.)

The drag coefficient of a stable bullet in air is an indicator of penetration potential
through solids.  A narrow stable full-jacket bullet has low drag in air, and is more
efficient in penetrating obstructions. They must then have remaining energy to
penetrate soft-tissue at least 5".

Expanding bullets limit soft tissue penetration, and can even prevent penetration.
Yaw (key-holing) reduces energy and penetration, and is no "advantage" unless
there are no obstructions and the target is close. (test those short-barrel guns)


Expanding or flat-nose bullets are not effective from short barrels ( < 2.5")
for 22lr, 32acp, 380acp, and other loads under 180 ftlb (from the actual barrel).

I would never use anything but FMJ in a low-energy pocket gun. (no flat nose)
A 9mm or 357 are different, but they tend to be too heavy and too large.
Maybe a 22wmr from a 4" barrel is good enough for flat/soft points.
(I will test in poplar cylinders someday, using 50gr subsonics if I can get them)

The 25acp should not be chosen for personal defense; it's just too weak through
leather and bone.  A 22lr-rn-hv can be effective if fired from a semi-auto barrel
that is least a 3" long, based on my tests on poplar wood.
           
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In 380 bullets, the center of pressure during yaw (pressure from air, leather, bone)
is substantially closer to the center of gravity than for the 32acp.
For a given barrel length, the 380 is less stable through all media, and a
short barrel increases this relative instability.

I saw a thread about frequent keyholing from a popular "high-end" pocket gun.
Their product site does not even reveal the barrel length. (which is 2.1").
.