I have a question on bullet travel for a .223. I'm shooting a 55gr sftpt out of an LMT Defender with a 16" barrel. I've got a IOR Valdada 1.5-8x scope mounted. The information I've read says to zero this scope at 200 yards. After a 200 yard zero, I step up and shot at 15 yards-expecting POI to be higher than the POI for the current zero. Except, my bullet impacted almost 8 inches low. Is this normal?