If you encounter a Marine target/sniper rifle with a set of bases that are crooked or canted, you can rest assured that the Marines did not mount those bases! As for the 1941A1 snipers, please don't anyone try to convince me that the Philadelphia Depot would have turned out shoddy or crappy work. They actually made the majority of the Mann-Niedner bases used on the A5's, and probably made the Unertl bases as well. They were world class machinists/gunsmiths - period. Every base would have been mounted identical to all the others. Every handguard would have looked like the others. They did not have a bunch of Privates mounting this stuff. Show me a documented 1941A1 Marine sniper rifle with a rear base not butted up to the rear base - just one.
jt