Yea, I think those calibres from longer barrels are about equivalent to a .30 carbine. Since it's not a popular calibre any more the last thing I can remember mentioning it was a pair of armor body plates from Vietman war. They were 2 plates, really curved and covering the whole chest and back, that are held on by a harness, and they were ceramic, the surface sort of looked like carbon fibre in the pictures. Just a guess but I think the plates would be level III or IV.