silver stacking with eagles, each coin weighing in differently... are they FAKE??

Today I bought 250 troy ounces of silver eagles.
I mean what the hell...right?

First thing I did; I check em for any zipperhead funky clones that might have managed to slither through ebay into this shop.


When I got home I weighed each coin on a gram scale.

note: The troy ounce (480 grains) is heavier than the avoirdupois ounce (437.5 grains). A grain is 64.79891 milligrams (mg); therefore one troy ounce is 31.1034768 grams (g).

I started with my first tube of 20.
Here is what i got.

different silver eagle weights within the same batch.

ranging from 31.15 to 31.44

Is this normal for silver eagles, or is the US of corp using tungsten in silver now?