Witness the "pink mist" when you splatter a varmint. It''s logical to assume that both the entrance area and the exit area would show some of that dispersion along with the wound path through the middle.
One of the significant problems though is the blood inside the cavity has to be assumed to be well contaminated. When you gut, the is no way to avoid contaminating OTHERWSE uncontaminated areas like the hams and tenderloins even in the case of a through the chest double lung shot.. I have never seen any Xray or otherwise analytical attempt at shedding light on that problem.
A couple of observations. The "red mist" from a prairie dog is visible because it's a liquid traveling through a gas (air). Inside an animal the bullet is a solid traveling through a combination of liquid, soilid tissue, and air. You can't just assume that they behave the same without some kind of evidence to back it up. In fact it's more logical to assume that they don't behave the same absent of evidence to the contrary.
Your second assumption is even more illogical. If blood inside the chest cavity was in fact "well-contaminated" and there was no way to avoid contaminating the meat when a hunter guts an animal then you would expect that lead to show up in people who consume the meat. But we don't see that. So it's more logical to assume that what you describe does not happen.
Once again I can't blame anyone for playing it safe by using copper bullets, it's not that big a deal. But that decision is not based on anything you can point to except caution.
Go look at the MnDNR Xrays of the sheep. To a point you are correct in that lead from disintegrating bullets does not travel the same way through muscle. The dynamic conditions of a bullet penetrating the chest of an animal and the introduction of air under the hide (demonstrated by the expansion of the hide outward from the body on both sides) is the means by which that lead n the Xrays gets dispersed. Go shoot a gallon jug full of water and measure the dispersion of the water all the way around the jug. The amount of water dispersed backwards in the direction from which the bullet came is pretty surprising. The same exact effect is visible to varying degrees with varmints depending on the hit, the bullet and the velocity. At those high velocities flesh and bone being largely water tends to act like water (surprise).
All of the studies I am aware of and have read include a substantial portion of shotgun pellet killed animals. Lead DOES react very differently at 600-800 FPS than it does at >2500 FPS. Even children learn very early on that the hard bits in their burgers are not to be eaten. The studies have not differentiated that lead that I have seen. <1000 FPS projectiles tend not to shed much if any weight in game. >2500 FPS projectiles do tend to do so and it tends to be in the 30-50 percent of initial weight range. Further, it tends also to be the very fine particulate that MnDNR found.
The MnDNR study was designed to inform us about the amount and nature of lead deposition in animals shot with typical hunting weapons, and is unique in that I know of no other so designed.
Lead is toxic in all forms. Lead in the body, particularly when it's a foreign body, may not produce damage because it is frequently walled off and isolated from the body. There is never any need for lead in the body. Why would someone willingly put a toxic substance into their body? Is the superiority of lead projectiles so marked that copper is ineffectual to any noticeable degree? Lead is not like substances that can be toxic at high levels, it is quite toxic at extremely low levels.. Lead accumulates, and it is not readily excreted.
Accepting any lead in your food is no different whatsoever that accepting that Jack In The Box solved their E Coli 0157:H7 problem by cooking the meat a little longer. Sooner or later it catches up with you. Same exact comparison. If they don't mix fecal matter with meat we don't get poisoned. If I don't put lead in my deer, I don't get poisoned. The meat industry put cows in feed lots and they do so for simple economic reasons. Wild game has virtually no 0157:H7 E Coli. Cows removed from a feedlot an put on grass have a reduction of 90% or more in fecal matter E Coli. Copper bullets perform as well or better than cup and core bullets at 300 yards and less. They cost a little more than they cheapest cup and cores and about the same as better cup and cores. There just isn't a good argument for me to put lead in my food. Not a difficult question at all.
