Does anyone know the difference between Nikon 40 and 44 objective outside edge size is? I gave my son a Tikka rifle which has a Nikon Buckmaster 3-9x40 and he wants to upgrade the scope to a Nikon Monarch 3-9x44. The rifle right now has the stock rings it came with and has 3/16" clearance between the barrel and the scope objective tube. Thanks, Tim