Hi Guys,
So, I've had my M&P 10 for about three months now. Got a great deal through Grab-a-gun down in Texas. The rifle functions well. No issues with loading/ejection of spent brass, but I do have two issues I don't know what to do about.

The biggest issue I am facing is that my first rounds land high, by as much as 6-8", coming down an inch or two each shot, until I have 4 or 5 rounds through the barrel. Then, I assume as the barrel warms up, it stays accurate. I can group sub-moa easily once I get the first several rounds through. Any thoughts as to why this is happening, or how to fix it?

For the record, I broke in the barrel as if it was match grade.

My second problem is that either during the loading or ejection process, the brass is getting a rub mark that is large enough that it makes me question using it for reloading. Again, any thoughts on how to make this go away?