never used the TNT's but have experience with the SX bullets and have had the same results when I pushed them over the recommended velocities, gray smoke and little fly speck holes at different positions around the target... would imagine it would be a prudent call to follow the factory recommendations... if they perform like the SX did you'll be pleased with them... never had one exit a groundhog... body shots and it'll completely disjoint a hog from the hydrostatic shock... like picking up a sack full of cooked oatmeal... nothing but mush inside...