To be honest with you, I never checked that oval gap lol. the first thing I noticed was the gap between the gearbox and hop up chamber when installing the Lonex Hop up Chamber and I just adjusted it so it was flush to the gear box and it started feeding flawlessly. lol.
http://www.aresairsoft.com/for%20web...xpose_plan.jpg
If you look at the link I attached above, it will show you the part #F91.