i agree with most of whats benn said....
other then a hole drilled doesnt weaken...yes,, it does...
next time you drive down the street...look at the sign post..at the base, youll see some holes.
thats so when its hit, it breaks off, at that point..
now.
a hole with chamfered edges, {rolled over} will tend to add strength, but only on a sheet metal, or flat steel type application.
example.
look at a high end mountain bike, BMX bike roll cage in a race car,ect. the gussets may have holes to lighten them, and are usually chamfered..
however.
holes drilled in the area for a rear target sight on a 1903. Mauser, ect, wont weaken it enough to be a safety issue.
you may, have an issue with a case head failure if the bolt sets back the safety lug into that part of the receiver, that being said, if that happens to 6-48 holes wont make much diffferance..
and any one who drills extra holes in a 1903A4 shoot be kicked in the biskets.