"...by filing it down..." Don't use a file. It's not accurate enough.
An NM front sight is 62 thou wide vs 72 thou for a standard sight. If you know a machinist, take off the front sight and have 5 thou removed from both sides of the blade and cold blue it. Just doing that will make a difference.
M1/M14 NM sights are pricey. If you can find 'em. Has a smaller aperture and finer adjustments.
Gunparts, when they have 'em, wants $28.95US for an old style aperture alone. $27.55US for a front sight. Listed under M1 Garand. You need the elevation pinion too, if you can find the aperture. Gunparts has no NM pinions.