I did some light testing with the silica 0.28s and regular white 0.28s and on a VFC Scar-L lower receiver which measures about 0.47 cm or 0.30 inches thick. The approximate FPS was 350-360 with 0.20s and was fired at point blank range
Regular White 0.28s
As you can see, the damage caused by the silica 0.28s wasn't that extensive, but enough to create prominent dents on the receiver and hairline fractures inside the receiver. The regular white 0.28s also caused dents on the receiver, but they were not as deep. They also caused hairline fractures inside the receiver, but that could have been because two of the shots were grouped very close together. Please remember that this test was at point blank range. Further testing is needed at different ranges to see the full effects.
There have been reports of regular white bbs (not sure which brand, weight or distance) penetrating and creating wholes in plastic black receivers on the field. So please take this into consideration.