I got to help with a "vest test" demonstration in 1997 where we shot some police trade-in vests from Second Chance with 45-70s, my .54 ML rifle (using ball and conical bullets), arrows, crossbow bolts, and .22 rimfires. We also did knife demonstrations. If you're thinking "Mythbusters", I'm OK with that,because these were NOT scientific tests; this was a buncha yahoos with vests, guns, and time on their hands. The vests were on torso targets that were in turn mounted on 2" x 2" posts placed in 5-gallon buckets of concrete. Trauma plates were in place for some of the tests, and distances were from 5 to 25 yards. The stand-out results, which were allegedly reported to Second Chance:
The .54 never penetrated the vests, but tended to break the posts, especially with Maxi-Balls. I theorize that the trauma plates helped the Maxis dump their energy into the target.
"Trapdoor" 500 gr. 45-70 loads acted a lot like the .54 slug loads. Marlin-level 350 gr. loads made hash out of the trauma plates. No penetration.
Arrows from my hunting bows, compound and recurve, were stopped by the trauma plate but zipped through the vest if there was no plate installed. Field points and cut-on-contact broadheads were used.
.22LRs were stopped, but .22 Magnum full-patch bullets got through.
Most knives would get through the vest, including a butter knife that had been sharpened on the sidewalk. The guy doing that part of the test has been into kendo his whole life, and teaches officer survival.
So, T&H, I figure if my .54 with loads that usually pass through an elk couldn't get through a mid-90s Second Chance vest, a muzzleloader using pure lead projectiles of any configuration is going to be embarrassed, too. But note those broken poles- that is BLUNT FORCE TRAUMA ON A STICK, BABY! Whoever gets whacked with a Maxi-Ball being pushed by 110 gr. of powder is going to barf up his spleen.