http://www.firearmstactical.com/briefs12.htm
From airweight snubbies not suited for use with +P loads .38 Special wadcutters outperform JHPs which don't expand.
"None of the Federal 110-grain JHP bullets expanded. Each bullet retained its pre-fired truncated cone shape. Our average penetration measurement is reasonably close to MacPherson's model for a 115-grain .38 caliber truncated cone bullet, propelled at 790 fps. Figure 10-3 Truncated Cone Bullet Penetration Depth (Curve D, p. 248) shows a model penetration depth of approximately 23 inches in standard ordnance gelatin and soft tissue.2 The 3-inch difference between our test results and MacPherson's model can be explained by the 5-grain difference in bullet weight, the inexact nature of our test method, and possible dynamic differences between an unexpanded open tip hollowpoint bullet versus the meplat of a closed tip TC bullet.
"Our average penetration result for the CCI 148-grain wadcutter bullet is identical to MacPherson's model. According to Figure 10-2 Cylinder Bullet Penetration Depth, Curve B (145-grain bullet, 780 fps), the model indicates a penetration depth of approximately 20 inches of standard gelatin or flesh (p. 247).2
"It appears the Federal 110-grain Personal Defense HydraShok bullet doesn't achieve sufficient velocity necessary to cause the bullet to expand, when fired out of a short 2-inch barreled revolver. Water usually produces slightly greater JHP bullet expansion than gelatin and soft tissue. Therefore, if a bullet doesn't expand in water, it is highly unlikely to expand in an attacker's body.
"The unexpanded, streamlined, and less wound efficient truncated cone shape allowed the light Federal 110-grain Personal Defense HydraShok bullet to penetrate as deeply as the heavier, cylindrical shaped CCI wadcutter bullet, although both were propelled at similar velocities...
References/End Notes:
1. According to Cotey: "Penetration in rows of water-filled, 2-quart (1.89 liter) cartons is approximately 1.5 times that which would occur in 10% 4 degrees C gelatin. Since a U.S. 2-qt. carton is 3.75 inches (9.525 cm) wide and 3.75/1.5 = 2.5, one simply multiples the number of the carton in the row from which a test bullet was recovered by 2.5 to determine approximate gelatin penetration in inches or by 6.35 for the reading in centimeter. For example, a shot recovered from carton #6 would correspond to a gelatin penetration depth of approximately 15 inches (38.1 cm). (Cotey, Gus Jr.:"Number 1 Buckshot, the Number 1 Choice." Wound Ballistics Review, 2(4): p. 11; 1996.)
2. MacPherson, Duncan: Bullet Penetration - Modeling the Dynamics and Incapacitation Resulting from Wound Trauma. Ballistic Publications, El Segundo, CA; 1994.