338 LAPUA is too big for a REM 700 action , when you open a rem bolt face to 338 LM you get only a very thin ring of steel around the case head
even if REM 700 action is strong , REM lugs design on REM 700 is not really design to hold big case / hight pressure , 300 ULTRA / 404 case is max for me and never forget it is very difficult to find a human head as spare part in your local emergency hospital .
best is to purchase a real big custom action or use 338/300 ULTRA in single shot on a rem long action , 300 ULTRA cases are far cheaper than 338LM case.
Good shooting
DAN TEC