Wow. Ball ammo is supposed to help feed itself given the shape of the nose of the bullet.
I've never seen ball ammo pushed so far into a case before. Try to determine if the bullets are being compressed below the feed ramp or above the ramp but right below the barrel chamber (breach face).
I hate to say it but I don't think polishing is going to fix this. If its not the magazine then the ramp itself is not within spec either itself or by its placement.
Also, next time I'd run that sucker "wet" like an AR if it were me. At least until she loosened up.
Other than not using WD40 inside the firing pin channel, maybe someone could advise you on the quantity of lubrication to use on a a new (pseudo) sub gun.
And we know, that we know, what we know,
but is it true?