"I’ve said it before, but keep in mind that 12 to 18 inches of penetration in gelatin is not the equivalent of 12 to 18 inches in living tissue. The gel is a consistent test medium that lets us compare one bullet to another. Historically, bullets that penetrate at least 12 inches in gel have a higher success rate in the real world than those that don’t. Service caliber bullets that go past 18 inches might over penetrate. With a .32 ACP, that’s not as likely."I will add only that the correlation is higher in regular 10% ordnance gelatin than it is in synthetic gelatin; in synthetic gel, bullets don't expand quite as well and therefore tend to penetrate more*, and this effect increases with the velocity of the bullet to the point that with rifle bullets there's next thing to zero correlation. This is a gross rule of thumb and you can get answers as to the why of it in the math-y posts of a thread at p-f, like this one.
(This is why I personally like to see something more like thirteen to slightly greater than sixteen inches in synthetic gel. My idea of an ideal synthetic gel performance, going off the bullets with good real world and ordnance gel performance, would be getting found, fully mushroomed, in the denim layer on the far side of a 16" block, or maybe an inch or so into the catch block if there's no denim on the far side.)
*Also, this difference between synthetic and ordnance gel is why trying to interpret yaw cycles or temporary cavities from synthetic stuff is bordering on tea leaf reading.
