I took my ACR to the range today to dial in my EOTech 553 w/ 3x magnifier. i noticed when shooting cold bore i could dial the site in on point. but when it got warm the point of impact would shift left a couple of inches @ 100 yards. i fould myself adjusting back and forth. is this normal? i just found it hard to get it dialed in when my POI was shifting as i was shooting. any comments or suggestions for getting my optic dialed in, please let me know.