Putting oil on ammo can result in Ka Booms. The cartridge case is supposed to expand slightly in the chamber, and should contract just before extraction. Putting oil on ammo is not recommended because, the theory goes, if there's oil on the ammo, now it may not expand properly. Or it may not expand uniformly if there's more oil on one side than the other. The burning powder is contained in a volume, and shape different than originally designed and Ka Boom! I would think it would take alot more oil to do this than anyone would really put on ammo, but I've heard the warning in many a reloading manual, so you've been warned.
Also oil on ammo is a magnet for dirt, dust, and particles. It would seem to be counter-productive to reliable feeding. If you have to lubricate your ammo, then you need better ammo, or a different gun (unless you have a .276 Pedersen or something that only works with lubricated ammo).
Ross