I load and shoot 221 in a Rem XP 100. Hodgdon lists a 50 gr Nos BT loaded with 13.5 gr of H110 at 2637. I've never checked them with a speedo, but will now. I bet that 16 gr load at 3600 had some pop. Maybe H110 is not an ideal powder for this one, I'm going to start some with 4227 and compare. Loading small cases leaves no room for carelessness.