Gary, throw the brass away that was fired in another rifle. Use only Remington brass that you started off new.
Huge difference in Rem and Lapua brass dimensions, Lapua is much larger, set that brass aside for now.
I fear that you have a brass bristle or something stuck in your chamber or a load of brass build up on your bolt face, you have to check those things out.
Do you have a decent tool to clean out the chamber well?
Range pick up brass needs to be sized with a small base sizer, but it is good thinking to start off with new brass in a new chamber or new gun. What if the range pick up brass was fired in an AR 10 or other military weapon with a HUGE chamber.
You are measuring the length, and you have to consider the Web dimension to the .0001. Often to get the web dimension to where the chamber likes it, you may have to bump the shoulder back .011....another set of problems.
Big lesson here for you, throw away the brass with an unknown history. Even if you use a small base sizer and get the brass serviceable, you still need to keep that brass segregated as brass swells back out over time.
