2006 RCM Logo Dif Weight And Thickness?

I have gone through over 200 lbs of pennies in the last couple of months, and it seems all the newer ones were like this, with their weights and thicknesses varying in this way. If you take any roll of pennies from the last 10 years of production and look at them together from the edge you'll see the thickness is all over the place. I would guess that they weren't too concerned about it at the mint, as all in all your talking about differences of only a tenth of a gram or so... Probably less quality control in the production of the planchet to save money. Also may have to do with trying to maintain the weight of the coin while using two different metals, zinc and steel, which are quite different in density.