I've never heard of a range that bans lead core 30 caliber ammo. are you sure the guy didn't think you were talking about penetrator ammo(black tip)?
what art said, a lot of factory ammo(and I think AE is among it) has slower burning powder so rather than hitting it's pressure apex halfway down the barrel, it hits it right at the muzzle where the gas port is and that excess pressure bends the op rod, you can use whatever bullet weight you want so long as it uses the right type of powder and loaded to the right pressure tolerances.
I'm no armorer so I can't tell you why your garand is not functioning but I would heavily advise you not to continue with the AE, get ammo that specifically states on the box that it's M1 safe.
ignore my complete lack of capitalization. I still have no problem correcting your grammar.
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